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 A027019 #7 Oct 21 2019 16:49:56 %S A027019 1,11,267,2620,16305,77040,303553,1055231,3358268,10039132,28714818, %T A027019 79649852,216360858,579601543,1538746237,4061993928,10685640859, %U A027019 28051744332,73551897971,192720956939,504774508726,1321827638248,3461013838244,9061623069576,23724397134644 %N A027019 a(n) = A027011(2n+1, n+4). %K A027019 nonn %O A027019 3,2 %A A027019 _Clark Kimberling_ %E A027019 More terms from _Sean A. Irvine_, Oct 21 2019