A363891 - OEIS

%I #20 Jun 27 2023 09:16:53

%S 0,2,0,7,0,10,0,13,5,16,0,19,0,35,0,25,0,28,16,31,0,42,0,56,0,40,0,43,

%T 22,65,0,49,0,77,0,55,0,80,28,61,11,64,0,98,0,95,0,73,34,76,0,104,0,

%U 147,0,85,0,88,40,91,0,125,28,140,0,114,0,103,46,140,0,109,0,192,0,115,0

%N Sum of divisors of 3*n-2 of form 3*k+2.

%H Seiichi Manyama, <a href="/A363891/b363891.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A078182(3*n-2).

%F G.f.: Sum_{k>0} (3*k-1) * x^(2*k)/(1 - x^(3*k-1)).

%t a[n_] := DivisorSum[3*n - 2, # &, Mod[#, 3] == 2 &]; Array[a, 100] (* _Amiram Eldar_, Jun 26 2023 *)

%o (PARI) a(n) = sumdiv(3*n-2, d, (d%3==2)*d);

%Y Cf. A363514, A363889, A363890.

%Y Cf. A078182, A359239.

%K nonn

%O 1,2

%A _Seiichi Manyama_, Jun 26 2023