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 A373542 #12 Jun 10 2024 10:01:55
%S A373542 1,1,1,-2,-11,-44,-59,-104,1513,-4976,14761,-1005344,-594659,
%T A373542 -120135872,-8409491,-19661062784,461914321,-4406419844864,8555830993,
%U A373542 -1268264427577856,-595229416379,-455779307821067264,-13631036685419,-200172063313066452992
%N A373542 Expansion of e.g.f. exp(x * sqrt(1-x^2)).
%F A373542 a(n) = n! * Sum_{k=0..floor(n/2)} (-1)^k * binomial(n/2-k,k)/(n-2*k)!.
%F A373542 a(n) == 1 mod 3.
%o A373542 (PARI) a(n) = n!*sum(k=0, n\2, (-1)^k*binomial(n/2-k, k)/(n-2*k)!);
%Y A373542 Cf. A190863.
%K A373542 sign
%O A373542 0,4
%A A373542 _Seiichi Manyama_, Jun 09 2024