A086156 - OEIS

A086156

a(n) = sigma(n^2) - n*sigma(n).

0, 1, 1, 3, 1, 19, 1, 7, 4, 37, 1, 67, 1, 63, 43, 15, 1, 145, 1, 121, 69, 139, 1, 211, 6, 189, 13, 199, 1, 661, 1, 31, 145, 313, 87, 475, 1, 387, 195, 337, 1, 1155, 1, 427, 241, 559, 1, 691, 8, 817, 319, 577, 1, 1171, 163, 519, 393, 877, 1, 2413, 1, 999, 345, 63, 213, 2599

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

LINKS

Michel Marcus, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A065764(n) - A064987(n). - Michel Marcus, Aug 23 2019

Sum_{k=1..n} a(k) ~ (5*zeta(3)/Pi^2 - Pi^2/18) * n^3. - Amiram Eldar, Dec 15 2023

MATHEMATICA

Table[DivisorSigma[1, w*w]-w*DivisorSigma[1, w], {w, 1, 256}]

PROG

(PARI) a(n) = sigma(n^2) - n*sigma(n); \\ Michel Marcus, Aug 23 2019