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 A349974 #10 Jul 09 2025 04:57:35
%S A349974 0,1,5,17,53,147,389,981,2401,5697,13293,30423,68745,153403,339195,
%T A349974 743169,1617857,3497875,7523697,16102889,34324847,72875031,154233691,
%U A349974 325388121,684664081,1436991619,3009410483,6289146455,13119434889,27319198507,56799400255,117916622547
%N A349974 a(n) = 1 + Sum_{k=0..n} (2*k - 1)*A349976(n, k).
%Y A349974 Cf. A349976, A349973.
%K A349974 nonn
%O A349974 0,3
%A A349974 _Peter Luschny_, Dec 10 2021, following a suggestion from _Alois P. Heinz_