A364102 - OEIS

%I #14 Jul 17 2023 00:59:51

%S 0,0,4,0,0,9,4,0,14,0,4,19,0,0,37,0,0,29,4,0,34,0,18,48,0,0,48,0,0,49,

%T 23,0,63,0,4,59,14,0,92,0,0,78,4,0,74,0,33,79,0,19,111,0,0,89,38,0,94,

%U 0,4,108,0,0,171,0,14,109,4,0,142,0,48,119,0,0,128,29,0,138,67,0,134,0,4,139,0,0

%N Sum of divisors of 5*n-3 of form 5*k+4.

%F a(n) = A284103(5*n-3).

%F G.f.: Sum_{k>0} (5*k-1) * x^(3*k) / (1 - x^(5*k-1)).

%t a[n_] := DivisorSum[5*n - 3, # &, Mod[#, 5] == 4 &]; Array[a, 100] (* _Amiram Eldar_, Jul 17 2023 *)

%o (PARI) a(n) = sumdiv(5*n-3, d, (d%5==4)*d);

%Y Cf. A364100, A364101, A364103.

%Y Cf. A284103, A359270, A364106.

%K nonn

%O 1,3

%A _Seiichi Manyama_, Jul 04 2023