A081867 a(n) = sigma_11(2n-1).

1, 177148, 48828126, 1977326744, 31381236757, 285311670612, 1792160394038, 8649804864648, 34271896307634, 116490258898220, 350279478046112, 952809757913928, 2384185839843751, 5559091947792280, 12200509765705830, 25408476896404832, 50542391825574576, 96549159399201744

Offset: 1

Author

Benoit Cloitre, Apr 12 2003

Keywords

• nonn

Crossrefs

Cf. A013959.

Programs

Mathematica

Table[DivisorSigma[11,2n-1],{n,20}] (* Harvey P. Dale, Jun 26 2012 *)

PARI

a(n) = sigma(2*n-1, 11); \\ Amiram Eldar, Jan 08 2025

Formula

Sum_{k=1..n} a(k) ~ c * n^12, where c = 691 * Pi^12 / 3742200 = 170.666988... . - Amiram Eldar, Jan 07 2025