A103637 a(n) = Sum_{d|n, d==1 mod 3} d^2.

1, 1, 1, 17, 1, 1, 50, 17, 1, 101, 1, 17, 170, 50, 1, 273, 1, 1, 362, 117, 50, 485, 1, 17, 626, 170, 1, 850, 1, 101, 962, 273, 1, 1157, 50, 17, 1370, 362, 170, 1717, 1, 50, 1850, 501, 1, 2117, 1, 273, 2451, 726, 1, 2890, 1, 1, 3026, 850, 362, 3365, 1, 117, 3722

Offset: 1

Author

Ralf Stephan, Feb 11 2005

Keywords

• nonn

Links

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

Programs

Mathematica

a[n_] := DivisorSum[n, #^2 &, Mod[#, 3] == 1 &]; Array[a, 100] (* Amiram Eldar, Jun 30 2023 *)

PARI

a(n) = sumdiv(n, d, (d%3==1)*d^2); \\ Seiichi Manyama, Jun 30 2023