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 A363969 #13 Jun 30 2023 15:36:11 %S A363969 1,1,5,1,10,5,17,1,30,10,37,5,50,17,78,1,82,30,101,10,142,37,145,5, %T A363969 179,50,226,17,226,78,257,1,330,82,350,30,362,101,454,10,442,142,485, %U A363969 37,632,145,577,5,642,179,762,50,730,226,830,17,946,226,901,78,962,257,1191,1,1148,330,1157,82 %N A363969 Expansion of Sum_{k>0} k^2 * x^(2*k-1) / (1 - x^(2*k-1)). %F A363969 a(n) = Sum_{d|n, d==1 mod 2} ((d+1)/2)^2. %t A363969 a[n_] := DivisorSum[n, ((# + 1)/2)^2 &, OddQ[#] &]; Array[a, 100] (* _Amiram Eldar_, Jun 30 2023 *) %o A363969 (PARI) a(n) = sumdiv(n, d, (d%2==1)*((d+1)/2)^2); %Y A363969 Cf. A001227, A113415. %Y A363969 Cf. A050999, A363974. %K A363969 nonn,easy %O A363969 1,3 %A A363969 _Seiichi Manyama_, Jun 30 2023