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%I #15 Jun 29 2023 08:22:53
%S 1,1,1,1,1,3,1,1,1,1,4,3,1,1,1,5,1,3,1,1,6,4,1,3,1,7,1,1,1,3,8,5,4,1,
%T 1,11,1,1,1,1,10,8,1,4,1,11,1,7,1,1,12,7,1,3,4,13,1,1,1,3,14,8,6,5,1,
%U 20,1,1,1,1,16,11,1,1,1,17,4,9,1,5,18,10,1,8,1,19,1,4,1,3,20,11
%N Expansion of Sum_{k>0} x^k / (1 - x^(5*k))^2.
%H Seiichi Manyama, <a href="/A363925/b363925.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = (1/5) * Sum_{d|n, d==1 mod 5} (d+4) = (4 * A001876(n) + A284097(n))/5.
%F G.f.: Sum_{k>0} k * x^(5*k-4) / (1 - x^(5*k-4)).
%t a[n_] := DivisorSum[n, # + 4 &, Mod[#, 5] == 1 &] / 5; Array[a, 100] (* _Amiram Eldar_, Jun 28 2023 *)
%o (PARI) a(n) = sumdiv(n, d, (d%5==1)*(d+4))/5;
%Y Cf. A363926, A363928, A363929.
%Y Cf. A001876, A284097.
%Y Cf. A363901, A363903.
%K nonn
%O 1,6
%A _Seiichi Manyama_, Jun 28 2023
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