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 A308304 #18 May 20 2019 09:04:14
%S A308304 1,0,1,0,24,0,3396,0,1706112,0,2277172800,0,6690143635200,0,
%T A308304 38006393154105600,0,380203596126189158400,0,
%U A308304 6242084318591496668160000,0,159215887013285165806891008000
%N A308304 a(n) = (i^n)*Sum_{k=0..n} B_k*|s(n+1,k+1)|*(n+1)^k.
%C A308304 |s(n,k)| is the unsigned Stirling number of first kind (see A008275), B_k is the Bernoulli number and i^2=-1. All even-indexed terms are positive integers, and the odd-indexed terms are zero. A generating function would be welcomed.
%H A308304 R. Gy, <a href="http://arxiv.org/abs/1902.09309">An aerated triangular array of integers</a>, arXiv: 1902.09309 [math.CO], 2019.
%o A308304 (PARI) a(n) = (I^n)*sum(k=0, n, bernfrac(k)*abs(stirling(n+1,k+1,1))*(n+1)^k); \\ _Michel Marcus_, May 19 2019
%Y A308304 Cf. A286483.
%K A308304 nonn
%O A308304 0,5
%A A308304 _René Gy_, May 19 2019