[seqfan] Re: Empirical relation for A180169: Sigma(A180162(n)), where A180162(n) is the smallest N such that sigma(N) is an nth power, or 0 if no such N can be found
Alexander P-sky
apovolot at gmail.com
Fri Feb 25 20:25:16 CET 2011
for
a(n+2) = -(4*(n - 12)*a(n - 1) - 3*(n - 10)*a(n + 1))/(n - 9),a(0)=1,
a(1)=2, a(2)=3
WolframAlpha gives
a(n) = (2^n (5*n-24)+2*(-1)^n)/(2* (n-11))
Alexander R. Povolotsky
On 2/25/11, Georgi Guninski <guninski at guninski.com> wrote:
> A180169: Sigma(A180162(n)), where A180162(n) is the smallest N such that
> sigma(N) is an nth power, or 0 if no such N can be found
>
> appears to satisfy for the first 465 terms (the B-File):
>
> a(n+2) = -(4*(n - 12)*a(n - 1) - 3*(n - 10)*a(n + 1))/(n - 9)
>
> this is the only potential relation involving sigma that i found.
>
> is there a fast ways to compute more terms to check?
>
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