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 A363030 #14 Jul 06 2023 07:30:02 %S A363030 1,2,4,4,6,6,8,8,12,10,12,12,14,14,19,18,18,18,20,20,26,22,26,24,26, %T A363030 26,36,28,30,32,32,32,40,34,36,36,40,42,50,40,42,42,44,46,54,46,48,48, %U A363030 55,50,66,52,54,54,60,56,68,60,60,66,62,62,78,64,68,66,68,68,82,70,84,78,74,74,92,76,78 %N A363030 Expansion of Sum_{k>0} k * x^k / (1 - x^(5*k-3)). %F A363030 a(n) = (1/5) * Sum_{d | 5*n-3, d==2 (mod 5)} (d+3). %F A363030 G.f.: Sum_{k>0} x^(2*k-1) / (1 - x^(5*k-4))^2. %t A363030 a[n_] := DivisorSum[5*n - 3, # + 3 &, Mod[#, 5] == 2 &]/5; Array[a, 100] (* _Amiram Eldar_, Jul 06 2023 *) %o A363030 (PARI) a(n) = sumdiv(5*n-3, d, (d%5==2)*(d+3))/5; %Y A363030 Cf. A359237, A363026. %K A363030 nonn %O A363030 1,2 %A A363030 _Seiichi Manyama_, Jul 06 2023