A081865 a(n) = sigma_7(2n-1).

1, 2188, 78126, 823544, 4785157, 19487172, 62748518, 170939688, 410338674, 893871740, 1801914272, 3404825448, 6103593751, 10465138360, 17249876310, 27512614112, 42637932336, 64340198544, 94931877134, 137293757384, 194754273882, 271818611108, 373845175782

Offset: 1

Author

Benoit Cloitre, Apr 12 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A013955.

Programs

Mathematica

DivisorSigma[7, Range[1, 45, 2]] (* Amiram Eldar, Aug 17 2019 *)

PARI

a(n) = sigma(2*n-1, 7); \\ Michel Marcus, Dec 04 2013

Formula

Sum_{k=1..n} a(k) ~ c * n^8, where c = 17 * Pi^8 / 10080 = 16.00248... . - Amiram Eldar, Jan 07 2025

Extensions

Three more terms from Michel Marcus, Dec 04 2013