Voozh

A046898

Partial sums of A046897.

1, 4, 8, 11, 17, 29, 37, 40, 53, 71, 83, 95, 109, 133, 157, 160, 178, 217, 237, 255, 287, 323, 347, 359, 390, 432, 472, 496, 526, 598, 630, 633, 681, 735, 783, 822, 860, 920, 976, 994, 1036, 1132, 1176, 1212, 1290, 1362, 1410, 1422, 1479, 1572, 1644, 1686, 1740, 1860

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

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..54.

Wikipedia, Jacobi four square theorem

FORMULA

G.f.: 1/(1 - q) * Sum_{k>=1} k * q^k / (1 + (-q)^k). - Seiichi Manyama, Jun 21 2024

MATHEMATICA

Accumulate[DivisorSum[#1, # &, Mod[#, 4] != 0 &] & /@ Range[50]] (* Jayanta Basu, Jun 30 2013 *)

PROG

(PARI) my(N=60, q='q+O('q^N)); Vec(sum(k=1, N, k*q^k/(1+(-q)^k))/(1-q)) \\ Seiichi Manyama, Jun 21 2024