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 A361815 #15 Mar 25 2023 13:20:11
%S A361815 1,2,2,-2,-14,-32,-30,64,346,752,584,-2044,-9486,-19324,-11368,66180,
%T A361815 271658,514916,192584,-2151612,-7949736,-13933280,-1779028,69933368,
%U A361815 235295106,378579404,-61171228,-2267724644,-7003832456,-10248117752,5236354188,73288104568
%N A361815 Expansion of 1/sqrt(1 - 4*x*(1-x)^2).
%C A361815 Diagonal of rational function 1/(1 - (1 - x*y) * (x + y)).
%H A361815 Seiichi Manyama, <a href="/A361815/b361815.txt">Table of n, a(n) for n = 0..1000</a>
%F A361815 a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(2*k,k) * binomial(2*k,n-k).
%F A361815 n*a(n) = 2 * ( (2*n-1)*a(n-1) - 2*(2*n-2)*a(n-2) + (2*n-3)*a(n-3) ) for n > 2.
%o A361815 (PARI) my(N=40, x='x+O('x^N)); Vec(1/sqrt(1-4*x*(1-x)^2))
%Y A361815 Cf. A085362, A110170, A162478, A359489, A359758, A360132, A361816, A361817.
%Y A361815 Cf. A137635.
%K A361815 sign
%O A361815 0,2
%A A361815 _Seiichi Manyama_, Mar 25 2023