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 A349973 #6 Dec 12 2021 21:08:00
%S A349973 0,1,4,12,34,89,226,554,1328,3104,7158,16235,36420,80797,177789,
%T A349973 387968,841696,1814473,3892920,8313588,17686711,37486091,79213997,
%U A349973 166888364,350720648,735273025,1538259673,3211682091,6693935172,13928034709,28936571039,60032053097
%N A349973 a(n) = Sum_{k=0..n} k*A349976(n, k).
%Y A349973 Cf. A349976.
%K A349973 nonn
%O A349973 0,3
%A A349973 _Peter Luschny_, Dec 12 2021