Convergence comparison test (sequence, calc II)

coals
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Homework Statement


Finally done with stupid improper integrals (calc 2 over summer is hard work, moving super fast) and now I'm sequences and series and what have you. I have another comparison test problem

Instructions are to find out if sequence converges or diverges, and find limit if it converges.

Sequence is:
{An}= n!/(2^n) .

The Attempt at a Solution


I know what to do with the factorial most of the time. I tried expanding it but the 2^n is throwing me off becuase the sequence diverges. Can i get a nudge in the right direction? I don't think my instructor wants me to find the limit of it if i can avoid doing so on divergence problems (he makes a point to tell us on HW to check convergence beforehand as practice for quizzes/tests).

As always thank all of you who help out pity-able college students as myself (lol) .
 
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You should really show us what you tried. But try a ratio test.
 
Its a sequence or a series ?
There is no comparison test for sequences.
If its a sequence: Try the sandwich theorem.
If its a series: See Dick's reply.
 
a_(n+1) / a_(n) >= 1, so the sequence monotonic increasing.
if you can't find a limit (number) then the series goes to infinity.
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...

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