This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A363925 #15 Jun 29 2023 08:22:53 %S A363925 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 A363925 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 A363925 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 A363925 Expansion of Sum_{k>0} x^k / (1 - x^(5*k))^2. %H A363925 Seiichi Manyama, <a href="/A363925/b363925.txt">Table of n, a(n) for n = 1..10000</a> %F A363925 a(n) = (1/5) * Sum_{d|n, d==1 mod 5} (d+4) = (4 * A001876(n) + A284097(n))/5. %F A363925 G.f.: Sum_{k>0} k * x^(5*k-4) / (1 - x^(5*k-4)). %t A363925 a[n_] := DivisorSum[n, # + 4 &, Mod[#, 5] == 1 &] / 5; Array[a, 100] (* _Amiram Eldar_, Jun 28 2023 *) %o A363925 (PARI) a(n) = sumdiv(n, d, (d%5==1)*(d+4))/5; %Y A363925 Cf. A363926, A363928, A363929. %Y A363925 Cf. A001876, A284097. %Y A363925 Cf. A363901, A363903. %K A363925 nonn %O A363925 1,6 %A A363925 _Seiichi Manyama_, Jun 28 2023