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 A027228 #9 Oct 25 2019 04:57:32
%S A027228 1,3,10,25,73,170,468,1050,2799,6138,16043,34644,89390,190913,488285,
%T A027228 1034228,2628861,5532322,14000177,29311171,73936801,154145390,
%U A027228 387911301,805899231,2024537328,4193625311,10521409964,21738996250
%N A027228 a(n) = Sum_{k=0..n} (k+1) * A026747(n, n-k).
%K A027228 nonn
%O A027228 0,2
%A A027228 _Clark Kimberling_