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 A366694 #9 Oct 17 2023 08:34:31
%S A366694 1,3,7,23,88,363,1576,7091,32768,154588,741442,3604495,17721394,
%T A366694 87960004,440165522,2218289051,11248850578,57354875692,293860786178,
%U A366694 1512169500356,7811933144432,40499933496818,210643657689644,1098802033533295,5747266778089846
%N A366694 G.f. satisfies A(x) = (1 + x)^2 + x*A(x)^2.
%F A366694 G.f.: A(x) = 2*(1+x)^2 / (1+sqrt(1-4*x*(1+x)^2)).
%F A366694 a(n) = Sum_{k=0..n} binomial(2*(k+1),n-k) * binomial(2*k,k)/(k+1).
%o A366694 (PARI) a(n) = sum(k=0, n, binomial(2*(k+1), n-k)*binomial(2*k, k)/(k+1));
%Y A366694 Cf. A025227, A366695.
%Y A366694 Cf. A086616.
%K A366694 nonn
%O A366694 0,2
%A A366694 _Seiichi Manyama_, Oct 16 2023