A103638 a(n) = Sum_{d|n, d==2 mod 3} d^2.

0, 4, 0, 4, 25, 4, 0, 68, 0, 29, 121, 4, 0, 200, 25, 68, 289, 4, 0, 429, 0, 125, 529, 68, 25, 680, 0, 200, 841, 29, 0, 1092, 121, 293, 1250, 4, 0, 1448, 0, 493, 1681, 200, 0, 2061, 25, 533, 2209, 68, 0, 2529, 289, 680, 2809, 4, 146, 3400, 0, 845, 3481, 429, 0, 3848

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Mathematica

a[n_] := DivisorSum[n, #^2 &, Mod[#, 3] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 30 2023 *)

Prog

(PARI) a(n) = sumdiv(n, d, (d%3==2)*d^2); \\ Seiichi Manyama, Jun 30 2023

Crossrefs

Sequence in context: A112149 A087736 A005075 * A129821 A126836 A055241

Adjacent sequences: A103635 A103636 A103637 * A103639 A103640 A103641

Keyword

nonn

Author

Ralf Stephan, Feb 11 2005

Status

approved