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 A027136 #10 Jun 26 2025 13:17:46
%S A027136 2,7,30,131,538,2153,8441,32484,123292,462673,1719899,6343170,
%T A027136 23237876,84641287,306758202,1106900323,3978716442,14252356483,
%U A027136 50897604269,181263039820,643928439234,2282348057593,8072881497390
%N A027136 a(n) = Sum_{k=0..n-1} T(n,k) * T(n,2n-k), with T given by A027113.
%Y A027136 Cf. A027113.
%K A027136 nonn
%O A027136 1,1
%A A027136 _Clark Kimberling_