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 A280655 #28 Jan 10 2024 16:05:06
%S A280655 0,3,11091,32104739,43189424229655,110209500084824275641,
%T A280655 17401090686295157740521962087,1341749054684714449837337405947519267,
%U A280655 416437630008271514606815213642830281374740126189,31880038884855523088456476438831355463732624957105297113285
%N A280655 Numerator of (Sum_{k=0..n^2-1} (-1)^k*sqrt(Pi)/(Gamma(1/2-k)*Gamma(1+k))) - n.
%C A280655 a(n) has at most n prime factors.
%F A280655 a(n)=Numerator of Sum_{k=0..n^2-1}(Binomial(2k,k)/4^k)-n.
%t A280655 Numerator[Table[Sum[Binomial[2k,k]/4^k,{k,0,n^2-1}]-n,{n,1,10}]]
%Y A280655 Cf. A280656 (denominators), A285388.
%K A280655 nonn,frac
%O A280655 1,2
%A A280655 _Ralf Steiner_, Apr 12 2017