A102359 - OEIS

A102359

a(n) = sigma((4^n - 1)/3), where sigma(n) is the sum of positive divisors of n.

%I #10 Feb 22 2020 02:30:07

%S 1,6,32,108,384,2688,5632,27864,153920,499968,1477440,11708928,

%T 22380544,115568640,620101632,1826150832,5726797824,54044390400,

%U 91626668032,555102471168,2352412508160,7458459886080,23955459951744,199536712962048,425355918188544,1849167560835072

%N a(n) = sigma((4^n - 1)/3), where sigma(n) is the sum of positive divisors of n.

%H Amiram Eldar, <a href="/A102359/b102359.txt">Table of n, a(n) for n = 1..603</a>

%F a(n) = A000203(A002450(n)). - _Amiram Eldar_, Feb 21 2020

%o (PARI) a(n) = sigma((4^n - 1)/3); \\ _Michel Marcus_, Feb 21 2020

%Y Cf. A000203, A002450.

%K nonn

%O 1,2

%A Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Feb 22 2005

%E More terms from _Amiram Eldar_, Feb 21 2020