A102360 - OEIS

A102360

a(n) = sigma((7^n - 1)/6), where sigma(n) is the sum of positive divisors of n.

%I #9 Feb 21 2020 09:29:37

%S 1,15,80,961,2802,52800,142020,2347506,10512320,96837120,329849040,

%T 8619170560,16148168402,221483030400,1146781040640,14442767744328,

%U 38774519976900,813898294809600,1904350030969680,35410174950039552

%N a(n) = sigma((7^n - 1)/6), where sigma(n) is the sum of positive divisors of n.

%H Amiram Eldar, <a href="/A102360/b102360.txt">Table of n, a(n) for n = 1..378</a>

%F a(n) = A000203(A023000(n)). - _Amiram Eldar_, Feb 21 2020

%o (PARI) a(n) = sigma((7^n - 1)/6); \\ _Michel Marcus_, Feb 21 2020

%Y Cf. A000203, A023000.

%K nonn

%O 1,2

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