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 A350503 #20 Aug 20 2025 09:14:17
%S A350503 1,10,81,826,9766,141448,2371173,46285454,1025108476,25583455958,
%T A350503 709014239914,21645251877538,721074846998772,26036416881319860,
%U A350503 1012400617533469985,42173042024213765280,1873237518724869171647,88367918629612594749582,4411615292876287372479856
%N A350503 Self-convolution of sigma_n(n).
%F A350503 a(n) = Sum_{k=1..n} A023887(k) * A023887(n-k+1).
%F A350503 a(n) ~ 2*n^n. - _Vaclav Kotesovec_, Aug 20 2025
%t A350503 Table[Sum[DivisorSigma[k, k]*DivisorSigma[n - k + 1, (n - k + 1)], {k, n}], {n, 20}]
%Y A350503 Cf. A023887 (sigma_n(n)).
%K A350503 nonn
%O A350503 1,2
%A A350503 _Wesley Ivan Hurt_, Jan 06 2022