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 A101800 #9 Aug 18 2024 14:10:46
%S A101800 0,1,16,2160,4644864,220962816000,126311423016960000,
%T A101800 97655159393202733056000000,2873961139404949958783139840000000000,
%U A101800 5118723340142578530942677236206891171840000000000
%N A101800 a(n)= abs(det[A000166(i+j+1)]), i,j=0...n, is the absolute value of the Hankel determinant of order n+1 of the derangements numbers, cf. A000166.
%C A101800 a(n) = abs(product( (p!)^2,p=0..n )*(n+1)!*LaguerreL(n+1,0,1)), n=0,1..., where LaguerreL(n,lambda,x) are generalized Laguerre polynomial.
%F A101800 a(n) = abs(A055209(n)*A009940(n+1)). [corrected by _Vaclav Kotesovec_, Feb 25 2019]
%t A101800 a[n_] := Table[Subfactorial[i+j+1], {i, 0, n}, {j, 0, n}] // Det // Abs;
%t A101800 Table[a[n], {n, 0, 9}] (* _Jean-François Alcover_, Aug 18 2024 *)
%Y A101800 Cf. A000166, A055209, A009940, A101799.
%K A101800 nonn
%O A101800 0,3
%A A101800 _Karol A. Penson_, Dec 17 2004