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 A380864 #11 Feb 08 2025 04:53:51
%S A380864 1,6,46,364,2902,23188,185420,1483096,11863910,94908420,759257636,
%T A380864 6074027496,48592102396,388736403144,3109889739352,24879112565936,
%U A380864 199032881137798,1592262978387044,12738103567806772,101904827587176776,815238617162887828,6521908924174861784
%N A380864 a(n) = [x^n] sqrt(1 - 4*x)/(1 - 8*x). Row sums of A380865.
%F A380864 a(n) = 4^n * Sum_{k=0..n} JacobiP(n - k, k + 1, -(n + 1/2), -1).
%F A380864 D-finite with recurrence: (-48+32*n)*a(n-2) + (6-12*n)*a(n-1) + n*a(n) = 0. - _Georg Fischer_, Feb 08 2025
%p A380864 gf := sqrt(1 - 4*x)/(1 - 8*x): ser := series(gf, x, 20): seq(coeff(ser, x, n), n=0..18);
%Y A380864 Cf. A380865.
%K A380864 nonn
%O A380864 0,2
%A A380864 _Peter Luschny_, Feb 06 2025