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 A174993 #12 Jul 22 2025 07:56:00
%S A174993 0,0,1,4,11,36,119,443,1718,7245,32313,153730,771677,4088053,22741818,
%T A174993 132596893,807840501,5132194862,33924901021,232905225561,
%U A174993 1657803862422,12215420390037,93042805475305,731622623516178,5931914758691917,49535825763153373,425606813712984146,3758735172560999933,34089943206777076429,317245175458777517030
%N A174993 a(n) = -Floor[n/2]! + Sum[(Eulerian[n - j, j]), {j, 0, Floor[n/2]}].
%F A174993 a(n)=-Floor[n/2]! + Sum[(Eulerian[n - j, j]), {j, 0, Floor[n/2]}]=A000800(n)-Floor[(n-1)/2]!
%t A174993 <<Combinatorica`
%t A174993 a = Table[-Floor[n/2]! + Sum[(Eulerian[n - j, j]), {j, 0, Floor[n/2]}], {n, 1, 30}]
%Y A174993 Cf. A000800.
%K A174993 nonn
%O A174993 1,4
%A A174993 _Roger L. Bagula_, Dec 02 2010