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 A356344 #7 Aug 05 2022 06:14:13
%S A356344 2,20,100,590,2102,13190,40646,233696,865756,4191364,12656548,
%T A356344 88372916,233981316,1196779716,4919600196,23553092286,65558004246,
%U A356344 419488280946,1126393556946,6915947767386,24140199749466,99887762443386,297490099905786,2232346320891786,6151075120462098
%N A356344 a(n) = Sum_{k=1..n} binomial(2*k, k) * sigma(k).
%C A356344 The average value of a(n) is Pi^(3/2) * sqrt(n) * 2^(2*n+1) / 9.
%t A356344 Table[Sum[Binomial[2*k, k]*DivisorSigma[1, k], {k, 1, n}], {n, 1, 30}]
%o A356344 (PARI) a(n) = sum(k=1, n, binomial(2*k, k) * sigma(k)); \\ _Michel Marcus_, Aug 05 2022
%Y A356344 Cf. A000203, A024916, A185003, A351146.
%K A356344 nonn
%O A356344 1,1
%A A356344 _Vaclav Kotesovec_, Aug 04 2022