Sequences Definition and 590 Threads

  1. Elm8429

    I Delta sequence "extrapolation"

    Studying delta sequences and am wondering if ##\phi_n(x)## is a delta sequence (it resembles and validates the sifting property), will ##\phi_n(x - a)## or ##\phi_n(whatever)## respect the sifting property ? I think I get confused in the semantics, because reading my textbook, I get the...
  2. chwala

    Solve the given problem involving probability without replacement

    Okay, i was able to solve it by trial and error, i am seeking for a more concrete approach. Can combination work here? or a more solid approach using sequences? or probability itself? My trial and error, ##P_{green} = \dfrac{9}{12}×\dfrac{8}{11} ×\dfrac{7}{10}×\dfrac{6}{9}×\dfrac{3}{8} =...
  3. P

    I Simple partitioning of sequence in Proposition 1.15 in Folland's text

    Below is Proposition 1.15 in Folland at the beginning of the section of Borel measures on ##\mathbb R## (he is trying to construct a measure from ##F##). Here the algebra ##\mathcal{A}## is the finite disjoint union of h-intervals, where h-interval is a set of the form ##(a,b]##, ##(a,\infty)##...
  4. Euge

    POTW What Is the Infimum of This Set of Superior Limits?

    Let ##\mathbb{R}^\omega_{+}## be the set of all sequences ##(a_n)_{n=1}^\infty## of positive real numbers. Determine the infimum $$\inf\left\{\limsup_{n \to \infty} \left(\frac{1 + a_{n+1}}{a_n}\right)^n : (a_n) \in \mathbb{R}^\omega_{+}\right\}$$
  5. P

    I How does the ratio test fail and the root test succeed here?

    The series that is given is $$\frac12+\frac13+\left(\frac12\right)^2+\left(\frac13\right)^2+\left(\frac12\right)^3+\left(\frac13\right)^3+\ldots.$$ Now, it's easy to see these are two separate geometric series, however, Spivak claims the ratio test fails because the ratio of successive terms...
  6. G

    Calculating Shannon Entropy of DNA Sequences

    Unfortunately, I have problems with the following task For task 1, I proceeded as follows. Since the four bases have the same probability, this is ##P=\frac{1}{4}## I then simply used this probability in the formula for the Shannon entropy...
  7. A

    Probability involving Gaussian random sequences

    How do I approach the following problem while only knowing the PSD of a Gaussian random sequence (i.e. I don't know the exact distribution of $V_k$)? Or am I missing something obvious? Problem statement: Thoughts: I know with the PSD given, the autocorrelation function are delta functions due...
  8. mcastillo356

    Why does this function make it easy to prove continuity with sequences?

    I've been given the proof, but don't understand; to calculate the limit of ##f## when ##x## tends to zero it's enough to see that if ##\{x_n\}_{n=1}^\infty## is a sequence that tends to ##0##, then...
  9. M

    B Golden Ratio in Collatz-like sequences

    Consider the following: We start with a positive integer: x If x is even, do x/2 If is odd, do Floor function( x * y) with y being some decimal number between 1 and 2 And repeat until a loop is reached. If 1 is reached, the next number will be 1 as well. So we reach a loop too. An example: x =...
  10. A

    Sinusoidal sequences with random phases

    Hello all, I have a random sequences question and I am mostly struggling with the last part (e) with deriving the marginal pdf. Any help would be greatly appreciated. My attempt for the other parts a - d is also below, and it would nice if I can get the answers checked to ensure I'm...
  11. Euge

    POTW Infinite Sequences of Sines

    Prove the existence of a strictly increasing sequence ##m_1 < m_2 < m_3 < \cdots## of integers satisfying the property that for all positive integers ##\ell##, the sequence ##\sin(\ell m_1), \sin(\ell m_2), \sin (\ell m_3),\ldots## converges.
  12. A

    Trust Fund problem using series and sequences

    I have tried inserting 0.955 in the above formula for the sum of a geometric series and setting it equal to 3,000,000 (S_n) with n =3. This did not work out well My second attempt was, considering that the payment is paid every year in the future, to use the convergence formula. There k = 0.955...
  13. Vividly

    B Understanding about Sequences and Series

    Homework Statement:: Tell me if a sequence or series diverges or converges Relevant Equations:: Geometric series, Telescoping series, Sequences. If I have a sequence equation can I tell if it converges or diverges by taking its limit or plugging in numbers to see what it goes too? Also if I...
  14. chwala

    Bounded and monotonic sequences - Convergence

    I would like some clarity on the highlighted part. My question is, consider the the attached example ##(c)##, This sequence converges ( by using L'Hopital's rule)...now my question is, the sequence is indicated on text as not being monotonic...very clear. Does it imply that if a sequence is not...
  15. A

    I Limits of Two Ordinal Sequences

    Let ##\omega_1## be the first uncountable ordinal such that ##x## is an element of ##\omega_1## if and only if it is either a finite ordinal or there exists a bijection from ##x## onto ##\omega##. I want to define a matrix such that the matrix contains each element of ##\omega_1## only once. To...
  16. BerriesAndCream

    Calculating nth Term of Sequences: What Now?

    I don't understand what the question is asking. the nth term of the first sequence i can calculate to be -2n+4, while 2n-24 is the nth term for the second sequence. now what? The question isn't clear.
  17. B

    Do Cauchy Sequences Imply Convergent Differences?

    I've started by writing down the definitions, so we have $$x_n-y_n\rightarrow 0\, \Rightarrow \, \forall w>0, \exists \, n_w\in\mathbb{N}:n>n_{w}\,\Rightarrow\,|x_n-y_n|<w $$ $$(x_n)\, \text{is Cauchy} \, \Rightarrow \,\forall w>0, \exists \, n_0\in\mathbb{N}:m,n>n_{0}\,\Rightarrow\,|x_m-x_n|<w...
  18. C

    MHB Upper Bound of Sets and Sequences: Analyzing Logic

    Upper bound definition for sets: $ M \in \mathbb{R} $ is an upper bound of set $ A $ if $ \forall \alpha\in A. \alpha \leq M$ Upper bound definition for sequences: $ M \in \mathbb{R} $ is an upper bound of sequence $ (a_n)$ if $ \forall n \in \mathbb{N}. a_n \leq M$ Suppose we look at the...
  19. yucheng

    Understanding the Use of Min in Cauchy Sequences

    I refer to this page: https://taoanalysis.wordpress.com/2020/03/26/exercise-5-3-2/ I am having trouble understanding the purpose / motivation behind using the min as in ##\delta := \min\left(\frac{\varepsilon}{3M_1}, 1\right)## and ##\varepsilon' := \min\left(\frac{\varepsilon}{3M_2}...
  20. yucheng

    Proof that two equivalent sequences are both Cauchy sequences

    Let us just lay down some definitions. Both sequences are equivalent iff for each ##\epsilon>0## , there exists an N>0 such that for all n>N, ##|a_n-b_n|<\epsilon##. A sequence is a Cauchy sequence iff ##\forall\epsilon>0:(\exists N>0: (\forall j,k>N:|a_j-a_k|>\epsilon))##. We proceeded by...
  21. A

    DNA sequencing and restoring malformed sequences

    I was just reading about DNA sequencing. In my view, DNA can be modeled into an ordered sequence of nucleobases, as if the two strands were joined into a single strand (just like in RNA). The first half of the sequence models the first strand. The four nucleobases are numbered from 0 to 3...
  22. Purpleshinyrock

    How to Solve Arithmetic Sequence Problems

    Summary:: Sequences, Progressions Hello. I have been Given the following exercise, Let (a1, a2, ... an, ..., a2n) be an arithmetic progression such that the sum of the last n terms is equal to three times the sum of the first n terms. Determine the sum of the first 10 terms as a function of...
  23. T

    I Limits of functions and sequences

    Hello there.Is there any function or sequence that has no limits at any point? I am not necessarily talking about functions on euclidean spaces, they could be on topological spaces in general.Also, we have homeomorphism that is about I think mostly continuity, diffeomorphism about...
  24. penroseandpaper

    Converging Vs diverging sequences

    A sequence is made up of two sequences an=(n^2)/(n+2) - (n^2)/(n+3) The problem asks for the solver to work out if it's converging or diverging, and find a limit if possible. My first thought was to write both over a common denominator and then divide through by the dominant term; this...
  25. I

    B Weird stuff on infinite numerical sequences in a Soviet book

    The book is Calculus: Basic Concepts for High School on the first page you are given the following sequence: 1, -1, 1/3, -1/3, 1/5, -1/5, 1/7, -1/7, ... several pages later the rule is given: in the second rule, for the first term in the sequence, the coefficient of one of the terms is 1/0...
  26. S

    I Convergence of sequences of functions with differing domains?

    Of the various notions of convergence for sequences of functions (e.g. pointwise, uniform, convergence in distribution, etc.) which of them can describe convergence of a sequence of functions that have different domains? For example, let ##F_n(x)## be defined by ##F_n(x) = 1 + h## where ##h...
  27. WMDhamnekar

    MHB Solve Math Problem: Mixing Milk & Water to Get 50% Milk

    Hi, A person has 40 litres of milk. As soon as he sells half a litre, he mixes the remainder with half a litre of water. How often can he repeat the process, before the amount of milk in the mixture is 50% of the whole? Detailed explanation is appreciated.:) Solution: I am working on...
  28. M

    MHB Topic of presentation: Elementary Geometry vs Fibonacci & its sequences

    Hey! 😊 Between the following two topics: Elementary Geometry Fibonacci and its sequences which would you suggest for a presentation? Could you give me also some ideas what could we the structure of each topic? :unsure:
  29. J

    MHB Number patterns and sequences - Tn Term

    The number sequence is as follows: 3x+5y; 5x; 7x-5y; 9x-10y... I need to formulate a general term - Tn=T1+d(n-1) In the above sequence I have no idea what. I also think this sequence is non linear. Please help with a solution Thanks
  30. sergey_le

    Proving inequalities for these Sequences

    I need help only in section 3 I have some kind of solution but I'm not sure because it seems too short and too simple. We showed in section 1 that an> 0 per n. Given that an + 1 <0 and an + 1 = an / a1 therefore a1 <0 is warranted
  31. M

    MHB Is the Convergence of These Sequences Correctly Determined?

    Hey! :o Check the below sequences for convergence and determine the limit if they exist. Justify the answer. $\displaystyle{f_n:=\left (1-\frac{1}{2n}\right )^{3n+1}}$ $\displaystyle{g_n:=(-1)^n+\frac{\sin n}{n}}$ I have done the following: $\displaystyle{f_n:=\left...
  32. Math Amateur

    MHB Understanding Andrew Browder's Prop 8.7: Operator Norm and Sequences

    I am reading Andrew Browder's book: "Mathematical Analysis: An Introduction" ... ... I am currently reading Chapter 8: Differentiable Maps and am specifically focused on Section 8.1 Linear Algebra ... I need yet further help in fully understanding the proof of Proposition 8.7 ...Proposition...
  33. Math Amateur

    MHB Understanding Proposition 8.7: Operator Norm and Sequences

    I am reading Andrew Browder's book: "Mathematical Analysis: An Introduction" ... ... I am currently reading Chapter 8: Differentiable Maps and am specifically focused on Section 8.1 Linear Algebra ... I need some further help in fully understanding the proof of Proposition 8.7 ...Proposition...
  34. F

    Solve Limits of Sequences: e2 when n=∞

    If n is ∞, then ln (n) = ln (∞) = ∞ Then, 1/∞ = 0 Any number raised to "0" = 1, so the answer should be 1. However the book says the answer is e2. Could you provide me some help?
  35. TytoAlba95

    How have scientists derived the gene sequences known today?

    I know that human genome sequencing was done by 2001. Inintially there were Maxam-Gilberth technique, then Sanger's technique and then finally NGS techniques have made sequening faster and efficient. My question is, though we are able to sequence the whole genome, how have scientists arrived at...
  36. Math Amateur

    MHB The Metric Space R^n and Sequences .... Remark by Carothers, page 47 ....

    I am reading N. L. Carothers' book: "Real Analysis". ... ... I am focused on Chapter 3: Metrics and Norms ... ... I need help with a remark by Carothers concerning convergent sequences in \mathbb{R}^n ...Now ... on page 47 Carothers writes the following: In the above text from Carothers we...
  37. Math Amateur

    MHB Why is the Series Absolutely Convergent for Sequences in l^2(N)?

    I am reading Houshang H. Sohrab's book: "Basic Real Analysis" (Second Edition). I am focused on Chapter 2: Sequences and Series of Real Numbers ... ... I need help with an aspect of Example 2.3.52 ... The start of Example 2.3.52 reads as follows ... ... In the above Example from Sohrab we...
  38. Math Amateur

    I Real Numbers & Sequences of Rationals .... Garling, Corollary 3.2.7 ....

    I am reading D. J. H. Garling's book: "A Course in Mathematical Analysis: Volume I: Foundations and Elementary Real Analysis ... ... I am focused on Chapter 3: Convergent Sequences ... ... I need some help to fully understand the proof of Corollary 3.2.7 ...Garling's statement and proof of...
  39. Math Amateur

    MHB Understanding Garling's Corollary 3.2.7 on Real Numbers and Rational Sequences

    I am reading D. J. H. Garling's book: "A Course in Mathematical Analysis: Volume I: Foundations and Elementary Real Analysis ... ... I am focused on Chapter 3: Convergent Sequences I need some help to fully understand the proof of Corollary 3.2.7 ...Garling's statement and proof of...
  40. V

    MHB GCD of Two Specified Sequences of Numbers: Conditions for Equality

    I consider two sequences of numbers $A=\{a_1,...,a_n\}$ and $B=\{k-a_1,...,k-a_n\}$, where $a_1 \le a_2 \le ... \le a_n \le k$. I am looking for such conditions under which: $gcd(a_1,...,a_n) = gcd(k-a_1,...,k-a_n)=1$. In more general form: $gcd(a_1,...,a_n) = gcd(k-a_1,...,k-a_n) \ge 1$. I...
  41. J

    MHB How to exclude combinations for defined sequences?

    Please can anyone help with the below problem? It’s an interesting problem but please bear with me as i don't have much math background. A factory’s product is sampled once per month every month by its quality inspection team. The factory is allowed up to 2 product failures per ROLLING 12...
  42. WMDhamnekar

    MHB Check Martingale Sequences from i.i.d. Variables | Stats SE

    How to answer this question $\rightarrow$https://stats.stackexchange.com/q/398321/72126
  43. F

    I Fisher matrix - equivalence or not between sequences

    I am currently studying Fisher's formalism as part of parameter estimation. From this documentation : They that Fisher matrix is the inverse matrix of the covariance matrix. Initially, one builds a matrix "full" that takes into account all the parameters. 1) Projection : We can then do...
  44. L

    A Same open sets + same bounded sets => same Cauchy sequences?

    Let ##d_1## and ##d_2## be two metrics on the same set ##X##. Suppose that a set is open with respect to ##d_1## if and only if it is open with respect to ##d_2##, and a set is bounded with respect to ##d_1## it and only if it is bounded with respect to ##d_2##. (In technical language, ##d_1##...
  45. Entertainment Unit

    Find bounding numbers for two interrelated sequences

    Homework Statement Let ##a## and ##b## be positive numbers with ##a \gt b##. Let ##a_1## be their arithmetic mean and ##b_1## their geometric mean: ##a_1 = \frac {a + b} 2## and ##b_1 = \sqrt{ab}## Repeat this process so that, in general ##a_{n + 1} = \frac {a_n + b_n} 2## and ##b_{n + 1} =...
  46. M

    B Recursive sequences - notation question

    I understand that when a sequence is described recursively, for example: ##a_1=2, a_{n+1} = \sqrt{3a_n}## then we mean that the first term is 2, the second term is ##\sqrt{3*2} = \sqrt{6}##, the third term is ##\sqrt{3*\sqrt{6}}##, and so on. What I do not understand is how to interpret the...
  47. Mr Davis 97

    Interior of the set of "finite" sequences

    Homework Statement Identify the boundary ##\partial c_{00}## in ##\ell^p##, for each ##p\in[1,\infty]## Homework Equations The interior of ##S## is ##\operatorname{int}(S) = \{a\in S \mid \exists \delta > 0 \text{ such that } B_\delta (a) \subseteq S\}##. ##\partial S = \bar{S}\setminus...
  48. S

    I Sequences for infinitely nested radicals

    In the thread https://www.physicsforums.com/threads/recursive-square-root-inside-square-root-problem.954655/ a sequence interpreted from the notation: ##\large{\sqrt{2+\pi \sqrt{3+\pi\sqrt{4+\pi\sqrt{5+\dotsb}}}}}## was discussed. What sequence would you (fellow forum members) associate with...
  49. Mr Davis 97

    Proving "Limits of Finite Sequences Implies Limit of Sum

    Homework Statement For each ##n\in\mathbb{N}##, let the finite sequence ##\{b_{n,m}\}_{m=1}^n\subset(0,\infty)## be given. Assume, for each ##n\in\mathbb{N}##, that ##b_{n,1}+b_{n,2}+\cdots+b_{n,n}=1##. Show that ##\lim_{n\to\infty}( b_{n,1}\cdot a_1+b_{n,2}\cdot a_2+\cdots+b_{n,n}\cdot a_n) =...
  50. Mr Davis 97

    Convergent sequences might not have max or min

    Homework Statement Prove or produce a counterexample: If ##\{a_n\}_{n=1}^\infty\subset \mathbb{R}## is convergent, then ## \min (\{a_n:n\in\mathbb{N}\} )## and ##\max (\{a_n:n\in\mathbb{N}\} ) ## both exist. Homework EquationsThe Attempt at a Solution I will produce a counterexample...
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