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 A027258 #8 Oct 26 2019 22:34:28
%S A027258 0,6,52,428,3552,29790,251980,2145822,18373296,158025186,1364247180,
%T A027258 11815188000,102606325136,893175905778,7791151047204,68086757974300,
%U A027258 595980599148672,5224392846601730,45857525238248604,402997448078904948,3545390129177031520,31221592914677352138
%N A027258 a(n) = Sum_{k=0..2n-1} T(n,k) * T(n,k+1), with T given by A025177.
%K A027258 nonn
%O A027258 1,2
%A A027258 _Clark Kimberling_
%E A027258 a(1) corrected and more terms from _Sean A. Irvine_, Oct 26 2019