Need help understanding off axis electromagnet field strength equation

[Jake110]

I have this equation for the magnetic field strength of an electromagnet but it’s in the form of multiple polynomials. Here is the page where they all are:

http://www.netdenizen.com/emagnet/offaxis/solenoidoffaxis.htm

since it gives values for e_8 and p_8 I tried using the main equation up to the 8th power but when I plotted the parallel distance against the field strength I found that it increases drastically to the point where at 5cm away the field strength is 1 Tesla (the strength I already know is B_0 which is the strength at the centre of the electromagnet and that’s only 0.03 Tesla)

So obviously the way I tried using it is wrong because the field strength should decrease the further away your measuring.

Can anyone help me figure out how to use this equation?

 

[Integral]

Read the page you linked carefully. Note that the polynomial represents approximately field strengths INSIDE the solenoid. As you have discovered, if you extrapolate polynomial approximations outside of the region it represents the values obtained become meaningless very fast,

 

[Jake110]

damit, you wouldn't happen to know an equation for the field strength outside the central core would you?