Monday, 9 December 2013

calculus - The series suminftyn=2frac1log(n!)




I'm trying to find out whether this Series
n=2an converges or not when
an=1log(n!)



I tried couple of methods, among them: d'Alembert an+1an, Cauchy condensation test n=22na2n, and they both didn't work for me.



Edit: I can't use stirling, and integral.



Thank you


Answer




Hint: You can use an=1logn!=1nk=1logk1nlogn.


Then use the Cauchy condensation test...


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