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 A027131 #7 Oct 23 2019 21:57:25
%S A027131 1,1,2,4,4,8,11,15,24,35,48,75,108,152,232,336,477,721,1046,1496,2245,
%T A027131 3264,4690,7006,10200,14709,21897,31916,46148,68523,99962,144841,
%U A027131 214634,313327,454756,672803,982718,1428225,2110278,3083747,4486717,6622251,9680743,14098072,20789712
%N A027131 a(n) = diagonal sum of left justified array T given by A027113.
%F A027131 a(n) = Sum_{k=0..n} A027113(n-k, k). - _Sean A. Irvine_, Oct 23 2019
%K A027131 nonn
%O A027131 0,3
%A A027131 _Clark Kimberling_
%E A027131 More terms from _Sean A. Irvine_, Oct 23 2019