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

1,2

Links

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

Formula

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

Prog

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

Crossrefs

Cf. A000203, A023000.

Sequence in context: A338414 A358917 A244855 * A375998 A372537 A344722

Adjacent sequences: A102357 A102358 A102359 * A102361 A102362 A102363

Keyword

nonn

Author

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

Status

approved