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 A380133 #7 Jan 13 2025 02:27:18
%S A380133 1,1,1,0,1,0,-9,70,-335,504,11935,-182094,1525833,-4911764,-99495473,
%T A380133 2430329070,-29988416159,158542630224,2868272912511,-102775471991126,
%U A380133 1714422613948345,-13166449628575404,-209400601689898289,10598981162761786950,-227206614609529433199
%N A380133 Expansion of e.g.f. sqrt(1 + 2*x*exp(x)).
%F A380133 a(n) = n! * Sum_{k=0..n} 2^k * k^(n-k) * binomial(1/2,k)/(n-k)!.
%o A380133 (PARI) a(n) = n!*sum(k=0, n, 2^k*k^(n-k)*binomial(1/2, k)/(n-k)!);
%Y A380133 Cf. A028310, A380134.
%Y A380133 Cf. A380050, A380093.
%Y A380133 Cf. A380015.
%K A380133 sign
%O A380133 0,7
%A A380133 _Seiichi Manyama_, Jan 12 2025