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 A230143 #13 Feb 19 2019 17:21:37
%S A230143 3,75,1785,333795,25638459,5788790007,898772045457,1467030741832227,
%T A230143 380324118068556519,244108884436744360605,94974266622893811200463,
%U A230143 58717088286185620331978925,95962705639251788100721754775,121363236202656183485569513082175
%N A230143 Denominator of 1/u_n(1/2), where polynomial u_n(x) is used to approximate x->sin(Pi*x)/Pi.
%C A230143 Coefficients of u_n are given by the n-th row of A144846/A144847.
%H A230143 Alois P. Heinz, <a href="/A230143/b230143.txt">Table of n, a(n) for n = 1..99</a>
%F A230143 Limit_{n->infinity} 1/u_n(1/2) = Pi.
%p A230143 u:= proc(n) option remember; local f, i, x; f:= unapply(simplify(sum('cat(a||(2*i+1)) *x^(2*i+1)', 'i'=0..n) ), x); unapply(subs(solve({f(1)=0, seq((D@@i)(f)(1)=`if`(i=1, -1, -(D@@i)(f)(0)), i=1..n)}, {seq(cat(a||(2*i+1)), i=0..n)}), sum('cat(a||(2*i+1)) *x^(2*i+1)', 'i'=0..n)), x) end: seq(denom(1/u(n)(1/2)), n=1..15);
%t A230143 u[n_] := u[n] = Module[{f, i, x, a}, f = Function[x, Sum[a[2*i+1]*x^(2*i+1), {i, 0, n}]]; Function[x, Sum[a[2*i+1]*x^(2*i+1), {i, 0, n}] /. First @ Solve[Join[{f[1] == 0}, Table[Derivative[i][f][1] == If[i == 1, -1, -Derivative[i][f][0]], {i, 1, n}]], Table[a[2*i+1], {i, 0, n}]]]]; Table[Denominator[1/u[n][1/2]], {n, 1, 15}] (* _Jean-François Alcover_, Feb 13 2014, after Maple *)
%Y A230143 Numerators are given in A230142.
%Y A230143 Cf. A000796.
%K A230143 nonn,frac
%O A230143 1,1
%A A230143 _Alois P. Heinz_, Oct 10 2013