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 A027291 #8 Oct 26 2019 23:09:10
%S A027291 1,3,8,16,39,77,179,354,799,1584,3504,6960,15174,30183,65085,129598,
%T A027291 277071,552140,1172348,2337624,4935586,9845978,20691318,41292196,
%U A027291 86432614,172538352,359934704,718680768,1494861996,2985378027
%N A027291 a(n) = Sum_{k=0..floor(n/2)+1} (k+1) * A026009(n, k).
%K A027291 nonn
%O A027291 0,2
%A A027291 _Clark Kimberling_