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 A380093 #9 Jan 12 2025 07:54:36
%S A380093 1,1,1,6,13,180,501,13720,34777,2014992,2512585,491642976,-564313947,
%T A380093 181714012480,-836832558275,95473740036480,-856984734161999,
%U A380093 68029327826567424,-954950936641491951,63368301861354866176,-1238053892876418633155,74904417332353810338816
%N A380093 E.g.f. A(x) satisfies A(x) = sqrt( 1 + 2*x*exp(x*A(x)) ).
%F A380093 a(n) = n! * Sum_{k=0..n} 2^k * k^(n-k) * binomial(n/2-k/2+1/2,k)/( (n-k+1)*(n-k)! ).
%o A380093 (PARI) a(n) = n!*sum(k=0, n, 2^k*k^(n-k)*binomial(n/2-k/2+1/2, k)/((n-k+1)*(n-k)!));
%Y A380093 Cf. A161631, A380094.
%Y A380093 Cf. A380035, A380050.
%K A380093 sign
%O A380093 0,4
%A A380093 _Seiichi Manyama_, Jan 12 2025