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 A255007 #6 Feb 16 2025 08:33:24
%S A255007 6,15,63,15,33,4095,3,255,3591,825,69,4095,3,435,21483,255,3,8636355,
%T A255007 3,33825,18963,345,141,69615,33,795,10773,435,177,425900475,3,255,
%U A255007 97083,15,2343,630453915,3,15,4977,575025,249
%N A255007 a(n) is the denominator of polygamma(2n+1, 1) / Pi^(2n+2).
%H A255007 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/PolygammaFunction.html">Polygamma Function</a>.
%H A255007 Wikipedia, <a href="http://en.wikipedia.org/wiki/Polygamma_function">Polygamma Function</a>.
%e A255007 Polygamma values {Pi^2/6, Pi^4/15, 8*Pi^6/63, 8*Pi^8/15, 128*Pi^10/33, ...} give numerators {1, 1, 8, 8, 128, ...} and denominators {6, 15, 63, 15, 33, ...}.
%t A255007 a[n_] := PolyGamma[2n+1, 1] / Pi^(2n+2) // Denominator; Table[a[n], {n, 0, 40}]
%Y A255007 Cf. A255006 (numerators).
%K A255007 nonn,frac,easy
%O A255007 0,1
%A A255007 _Jean-François Alcover_, Feb 12 2015