Find the interval of convergence for [(xn)^n]/(2^n * n!)

I've actually tried both methods but they contradict each other! For the root test I got x = 0 and for the ratio test I got x = e/2.

What's going on?

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- Mar 25th 2009, 09:24 AMKaitosanHuh? Ratio test contradicts root test?
Find the interval of convergence for [(xn)^n]/(2^n * n!)

I've actually tried both methods but they contradict each other! For the root test I got x = 0 and for the ratio test I got x = e/2.

What's going on? - Mar 25th 2009, 11:15 AMPlato
- Mar 25th 2009, 11:38 AMKaitosan
LOL. I suppose that's my mistake. I thought it was one because the exponent turns into zero. Oh well. Hey, will you please explain how that expression equals zero? Thanks.

- Mar 25th 2009, 11:40 AMmatheagle
try (rod) stirling's approximation of n!

http://en.wikipedia.org/wiki/Stirling's_approximation - Mar 25th 2009, 01:07 PMKaitosan
Jeez, I had no idea of this stuff. Thanks guys. :)