A103637 - OEIS

%I #10 Jun 30 2023 12:44:25

%S 1,1,1,17,1,1,50,17,1,101,1,17,170,50,1,273,1,1,362,117,50,485,1,17,

%T 626,170,1,850,1,101,962,273,1,1157,50,17,1370,362,170,1717,1,50,1850,

%U 501,1,2117,1,273,2451,726,1,2890,1,1,3026,850,362,3365,1,117,3722

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

%H Seiichi Manyama, <a href="/A103637/b103637.txt">Table of n, a(n) for n = 1..10000</a>

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

%o (PARI) a(n) = sumdiv(n, d, (d%3==1)*d^2); \\ _Seiichi Manyama_, Jun 30 2023

%K nonn

%O 1,4

%A _Ralf Stephan_, Feb 11 2005