A103638 - OEIS

%I #11 Jun 30 2023 12:45:34

%S 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,

%T 680,0,200,841,29,0,1092,121,293,1250,4,0,1448,0,493,1681,200,0,2061,

%U 25,533,2209,68,0,2529,289,680,2809,4,146,3400,0,845,3481,429,0,3848

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

%H Seiichi Manyama, <a href="/A103638/b103638.txt">Table of n, a(n) for n = 1..10000</a>

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

%o (PARI) a(n) = sumdiv(n, d, (d%3==2)*d^2); \\ _Seiichi Manyama_, Jun 30 2023

%K nonn

%O 1,2

%A _Ralf Stephan_, Feb 11 2005