Natural numbers Definition and 143 Threads

This may have already been found by many people but I discovered the pattern on my own out of curiosity with some coding. There are only 4 natural numbers whose factorial contains the same number of digits as the number itself. That is to say n = digits_in(n!). The trivial case is obviously...

Was fooling around and wrote down these two equations today that appear to work. I'm not all that bright and I'm positive these either have some proof or restate some conjecture--probably something in a textbook. Could somebody help me out? \forall n \in \mathbb{N}_0\smallsetminus\{0\} n^2 =...

1) Two sets have the same cardinality if there exists a bijection (one to one correspondence) from ##X## to ##Y##. Bijections are both injective and surjective. Such sets are said to be equipotent, or equinumerous. (credit to wiki) 2) ##|A|\leq |B|## means that there is an injective function...

w = {0,0 | 1,1 | 2,2...} Let x = number of primes up to w+1 Let y = number of primes up to w-1 Now there's an empty prime box in the 0,0 slot not connected to anything. So I let x = p-1 and y = p+1 p = [p0, p1, p2...] Now p0 becomes 1,0/1 It can be either on or off. For the sake of...

I screenshot https://math.stackexchange.com/q/4185842.

Hey! :giggle: How can we calculate the number of natural numbers between $2$ and $n$ that have primitive roots? Let $m$ be a positive integer. Then $g$ is a primitive root modulo $m$, with $(g,m)=1$, if the modulo of $g\in (Z/m)^{\star}$ is a generator of the group. We have that $g$ is a...

The number of even natural numbers less than 100000 that can be formed from the digits of the set (0,1,2,3,4,5,6) so that the digits in the number are not repeated is? Here I understand that the even number in the last place is an even number, that is, it has 4 possibilities, but won't the...

Prove for all $n\in N$ $\dfrac{|a_1+...a_n|}{1+|a_1+...+a_n|}\leq\dfrac{|a_1|}{1+|a_1|}+...\dfrac{|a_n|}{1+|a_n|}$

I have seen a solution for this question which was as follows, first out of 15 elements, take away 5, thus there are 11 gaps created for the remaining 10 numbers (say N) as, _N_N_N_N_N_N_N_N_N_N_ now, now we can insert back the 5 to comply with the non-consecutive stipulation for which, number...

Hi, I've seen several videos and documents that state that "the sum of all natural numbers is equal to -1/12". The "proof" in general is using ramanjuan summation and analytic continuation of the riemann function. In this proof, the election of the riemann function in order to perform the...

Homework Statement Prove that if a set A of natural numbers contains n_0 and contains k+1 whenever it contains k, then A contains all natural numbers ≥ n_0Homework EquationsThe Attempt at a Solution I'm just confused by the question, please don't answer it. Logically it makes sense that if n_0...

Homework Statement Find the number of natural numbers n such that (n2-900)/ (n-100) is an integer.Homework EquationsThe Attempt at a Solution I have done the following: (n2-900-9100+9100)/ (n-100) or,{ (n2 - (100)2) + 9100 }/ (n-100) or, (n+100) + (9100)/(n-100) I hope you can understand this...

Homework Statement Prove that ##\forall n \in \mathbb{N}## $$\frac{n}{2} < 1 + \frac{1}{2} + \frac{1}{3} + \ldots + \frac{1}{2^n - 1} \leq n \text{ .}$$ Homework Equations Peano axioms and field axioms for real numbers. The Attempt at a Solution Okay so my first assumption was that this part...

So I was just writing a proof that every natural number is either even or odd. I went in two directions and both require that 1 is odd, in fact I think that 1 must always be odd for every such proof as the nature of naturals is inductive from 1. I am using the version where 1 is the smallest...

Say you have an orange and a banana. You can say that they are two fruits. But this pertains to the categorization of fruit, which could be considered a mental construct of a category. You cannot say that you have two yellow objects, because you really don't. Relative to the category of color...

Find all natural numbers $n$, for which: \[\sqrt{1 \underbrace{4...4}_{n \: times}} \in \Bbb{N}\]

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.3.7 ... Theorem 1.3.7 and the start of the proof reads as follows: n the above proof we...

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.3.7 ... Theorem 1.3.7 and the start of the proof reads as...

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.2.10 ... Theorem 1.2.10 reads as follows: Towards the end (second last line) of the...

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.2.10 ... Theorem 1.2.10 reads as follows: Towards the end (second last line) of the...

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.2.7 (1) ... Theorem 1.2.7 reads as follows: https://www.physicsforums.com/attachments/6976...

I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Chapter 1: Construction of the Real Numbers ... I need help/clarification with an aspect of Theorem 1.2.7 (1) ... Theorem 1.2.7 reads as follows: In the above proof of (1) we read the...

Given any finite set of natural numbers, it seems evident that the odd numbers form a subset of the natural numbers. But what happens "at infinity"? I mean, if we account for all infinitely many natural numbers, there would be also infinitely many odd numbers. In such case, is it still true that...

By definition, the characteristic of a field is the smallest number of times one must use the ring's multiplicative identity element (1) in a sum to get the additive identity element (0). Can we use the same rule for the set of natural numbers? If yes, I found a problem, that has something to...

Hi, I hoping someone might be kind enough to possibly tell me where I have made an error :) I'm more of a recreational maths person, lol - and I'm trying to make a scheme that 'maps' any decimal number to a natural one. The method I have come up with is a bit odd, I'm hoping it works but still...

Homework Statement Prove that there doesn't exist natural numbers x and y such that the statement holds true. y^5 + 1 = (x^7-1)/(x-1)The Attempt at a Solution I was able to simplify the term down to y^5 / x = x^5 + (x^5-1)/(x-1) Not sure what to do with it

Here is a problem I am working on: Using the Rule of Sarrus: $$\begin{vmatrix} x & y & z \\ z & x & y \\ y & z & x \\ \end{vmatrix} =x^3+y^3+z^3-3xyz,$$ find $x, y, z$ such that $x^3+y^3+z^3-3xyz = 315.$ And here is what I have gotten so far: By row and column operations and by factoring out...

What does the N^2 mean in this case? (Image below) Does it mean, for all two pairs of natural numbers, a and b? How would I represent non pair numbers, i.e. how would I write "For integers k,l, and m such that k>1, l>2, m>k+l" all in one line?

Hello everyone. I wanted to prove the following theorem, using the axioms of Peano. Let ##a,b,c \in \mathbb{N}##. If ##ac = bc##, then ##a = b##. I thought, this was a pretty straightforward proof, but I think I might be doing something wrong. Proof: Let ##G := \{c \in \mathbb{N}|## if ##a,b...

Hi, New member here and have been dabbling with some aspects of George Cantor's work. I think I have found a way to put the irrationals in one to one correspondence with natural numbers but thousands of mathematicians over the years might disagree. Is there a subtle error ( or even a blatant...

Is there a term used to describe all number except the natural numbers?

Find all the natural numbers $a$ and $b$ such that $(a^2+1)(b^2+1)+45=2(2a+1)(3b+1)$.

Find the solutions in natural numbers for the following equation: \frac{10}{x+10}+\frac{10\cdot 9}{(x+10)(x+9)}+\cdots+\frac{10\cdot 9\cdot 8 \cdots\cdot 3 \cdot 2 \cdot 1}{(x+10)(x+9)(x+8)\cdots(x+3)(x+2)(x+1)}=5

Hello, At my exam I had to proof the title of this topic. I now know that it can easily be done by making a bijection between the two, but I still want to know why I didn't receive any points for my answer, or better stated, if there is still a way to proof the statement from my work. My work...

Hi, How and why set of natural numbers is closed?

Homework Statement [/B] I'm working through a problem in Abott's Understanding Analysis, second edition, the statement of the problem being: "Fix a member n of the natural numbers and let An be the algebraic numbers obtained as roots of polynomials with integer coefficients that have degree n...

Hi, I've seen on on several sites that you can prove that nCr, where r<=n, is a natural number. I'm not sure how to do this by induction. So I need help on this proof. How do I write this as a mathematical statement at the start of the induction proof? Thank you

I'm not a logician or mathematician but a philosopher (with dyscalculia) so please forgive me for skipping the technicalities... My question is this: Is there in the theory of non-well-founded sets (hypersets) something analogous to the set-theoretic construction of the natural numbers in ZF...

Homework Statement I am trying to understand why ℕ the set of natural numbers is considered a Closed Set. 2. Relevant definition A Set S in Rm is closed iff its complement, Sc = Rm - S is open. The Attempt at a Solution I believe I understand why it is not an Open Set: Given that it...

Hello! (Smile) Proposition: Each subset of the natural numbers is finite or countable. Proof: Let $X \subset \omega$. First case: $X$ is bounded. That means that $(\exists k \in \omega)(\forall y \in X) y \leq k$. Then $X \subset k+1$ and $X$, as a subset of a finite subset, is finite ...

Hello! (Wave) For each pair of natural numbers $m \in \omega, n \in \omega$ we define: $$m+0=m\\m+n'=(m+n)'$$ We fix a $m$ and recursively the operation $m+n$ is defined for any $n \in \omega$. Knowing for example that $m+0=m$ we can conclude what $m+1$ means. $$m+1=m+0'=(m+0)'=m'$$ and...

Hello! (Wave) I want to prove that for any natural numbers $n,m$ it holds that: $$n \subset m \leftrightarrow n \in m \lor n=m$$ $"\Leftarrow"$: Using the sentence: "For any natural numbers $m,n$ it holds that $n \in m \rightarrow n \subset m$" if $n \in m \lor n=m$, we conclude that $n...

I need a proof that the set of natural numbers with the the relationship of divisibility form a distributive lattice with gcd as AND and lcm as OR. I know it can be shown that a AND (b OR c) >= (a AND b) OR (a AND c) for a general lattice, and that if we can show the opposite, that a AND (b OR...

I am writing this in C#. Here is the code. using System; namespace ConsoleApplication3 { class Program { static void Main(string[] args) { int sum = 0; int uservalue; Int32.TryParse(Console.ReadLine(),out uservalue)...

I'm having trouble solving the equation m2 - n2 = 707, where n and m are natural numbers. Because there are 2 variables, even though they are discrete, the obvious thing to do would be to use another equation to solve for one of the variables and then insert the new form to the original...

Find all values of $x$ such that $f(x)=x^2-19x+99$ is a perfect square for all $x\in N$.

Is the set of the natural Nos complete?

Here is the question: I have posted a link there to this question so the OP can view my work.

Find natural numbers a and b such that $2^a-3^b = 7$

An easy question. All "odd" number can be expressed as a sum of consecutive natural numbers. Example: 35=17+18 35=5+6+7+8+9 35=2+3+4+5+6+7+8Question: Demonstrate that prime numbers (except for the "2"), can only be expressed as the sum of two consecutive natural numbers.