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 A280656 #19 Dec 12 2023 18:30:46
%S A280656 1,16,32768,67108864,70368744177664,147573952589676412928,
%T A280656 19807040628566084398385987584,1329227995784915872903807060280344576,
%U A280656 365375409332725729550921208179070754913983135744,25108406941546723055343157692830665664409421777856138051584
%N A280656 Denominator of (Sum_{k=0..n^2-1} (-1)^k*sqrt(Pi)/(Gamma(1/2-k)*Gamma(1+k))) - n.
%C A280656 a(n) is a power of 2.
%F A280656 a(n)=Denominator of Sum_{k=0..n^2-1}(Binomial(2k,k)/4^k)-n.
%t A280656 Denominator[Table[Sum[Binomial[2k,k]/4^k,{k,0,n^2-1}]-n,{n,1,10}]]
%Y A280656 Cf. A280655 (numerators).
%K A280656 nonn,frac
%O A280656 1,2
%A A280656 _Ralf Steiner_, Apr 12 2017