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%I #14 Jun 30 2023 08:36:11
%S 0,1,0,1,0,1,2,1,0,1,0,4,0,3,0,1,4,1,0,1,2,6,0,4,0,1,6,3,0,1,0,8,0,5,
%T 2,4,8,1,0,1,0,12,0,6,0,1,10,4,2,1,4,12,0,7,0,3,12,1,0,4,0,14,2,8,0,6,
%U 14,5,0,3,0,19,0,9,0,1,18,1,0,1,6,18,0,15,4,1,18,6,0,1,2,20,0
%N Expansion of Sum_{k>0} x^(2*k) / (1 - x^(5*k))^2.
%H Seiichi Manyama, <a href="/A363926/b363926.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = (1/5) * Sum_{d|n, d==2 mod 5} (d+3) = (3 * A001877(n) + A284280(n))/5.
%F G.f.: Sum_{k>0} k * x^(5*k-3) / (1 - x^(5*k-3)).
%t a[n_] := DivisorSum[n, # + 3 &, Mod[#, 5] == 2 &] / 5; Array[a, 100] (* _Amiram Eldar_, Jun 28 2023 *)
%o (PARI) a(n) = sumdiv(n, d, (d%5==2)*(d+3))/5;
%Y Cf. A363925, A363928, A363929.
%Y Cf. A001877, A284280.
%K nonn
%O 1,7
%A _Seiichi Manyama_, Jun 28 2023
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