A102360 a(n) = sigma((7^n - 1)/6), where sigma(n) is the sum of positive divisors of n.

1, 15, 80, 961, 2802, 52800, 142020, 2347506, 10512320, 96837120, 329849040, 8619170560, 16148168402, 221483030400, 1146781040640, 14442767744328, 38774519976900, 813898294809600, 1904350030969680, 35410174950039552

Offset: 1

Author

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

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..378

Crossrefs

Cf. A000203, A023000.

Programs

PARI

a(n) = sigma((7^n - 1)/6); \\ Michel Marcus, Feb 21 2020

Formula

a(n) = A000203(A023000(n)). - Amiram Eldar, Feb 21 2020