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 A375276 #9 Aug 09 2024 10:07:51
%S A375276 1,2,6,24,92,360,1448,5888,24144,99744,414432,1729920,7249088,
%T A375276 30476416,128487552,543014912,2299764992,9758138880,41473582592,
%U A375276 176530905088,752401603584,3210723420160,13716154361856,58653842276352,251049168687104,1075442759868416
%N A375276 Expansion of 1/sqrt(1 - 4*x - 8*x^3 + 4*x^4).
%F A375276 n * a(n) = 2*(2*n-1)*a(n-1) + 4*(2*n-3)*a(n-3) - 4*(n-2)*a(n-4).
%F A375276 a(n) = Sum_{k=0..floor(n/2)} 2^(n-k) * binomial(n-k,k)^2.
%o A375276 (PARI) my(N=30, x='x+O('x^N)); Vec(1/sqrt(1-4*x-8*x^3+4*x^4))
%o A375276 (PARI) a(n) = sum(k=0, n\2, 2^(n-k)*binomial(n-k, k)^2);
%Y A375276 Cf. A108485.
%K A375276 nonn
%O A375276 0,2
%A A375276 _Seiichi Manyama_, Aug 09 2024