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 A130426 #8 Sep 16 2015 12:39:09
%S A130426 1,2,12,72,1080,129600,54432000,22861440000,9601804800000,
%T A130426 4032758016000000,18631342033920000000,86076800196710400000000,
%U A130426 5169772619814426624000000000,310496543546054463037440000000000
%N A130426 a(n) = denominator of Sum_{k=1..n} 1/k^(n+1-k).
%t A130426 Table[Denominator[Sum[1/k^(n + 1 - k), {k, 1, n}]], {n, 1, 20}] (* _Stefan Steinerberger_, May 30 2007 *)
%Y A130426 Cf. A130425, A003101.
%K A130426 frac,nonn
%O A130426 1,2
%A A130426 _Leroy Quet_, May 26 2007
%E A130426 More terms from _Stefan Steinerberger_, May 30 2007