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 A356341 #7 Aug 05 2022 06:11:05
%S A356341 2,22,131,806,3607,20395,84254,422230,1842359,8616007,33843614,
%T A356341 173724659,676938316,2983855666,12806013721,57981927158,223432922515,
%U A356341 1040923729567,4004885305320,18277809794671,75668287229078,317458937099194,1215454524390767,5785782106653667
%N A356341 a(n) = Sum_{k=1..n} binomial(2*n, k) * sigma(k).
%F A356341 a(n) ~ Pi^2 * n * 4^(n-1) / 3.
%t A356341 Table[Sum[Binomial[2*n, k]*DivisorSigma[1, k], {k, 1, n}], {n, 1, 30}]
%o A356341 (PARI) a(n) = sum(k=1, n, binomial(2*n, k) * sigma(k)); \\ _Michel Marcus_, Aug 05 2022
%Y A356341 Cf. A000203, A024916, A185003, A351146.
%K A356341 nonn
%O A356341 1,1
%A A356341 _Vaclav Kotesovec_, Aug 04 2022