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 A321511 #15 Feb 19 2025 12:11:08
%S A321511 0,0,0,1,18,309,6716,213308,10809896,911472580,129530643900,
%T A321511 31095704935575,12611311380675900,8639383512070631700,
%U A321511 9995541355360989190800,19529076234659969430529200,64427185703425668434106855840,358869201916137601091798728321296
%N A321511 Number of alternating sign n X n matrices excluding permutation matrices.
%H A321511 Michael De Vlieger, <a href="/A321511/b321511.txt">Table of n, a(n) for n = 0..93</a>
%H A321511 Paul Barry, <a href="https://arxiv.org/abs/2104.01644">Centered polygon numbers, heptagons and nonagons, and the Robbins numbers</a>, arXiv:2104.01644 [math.CO], 2021.
%H A321511 Paul Barry, <a href="https://doi.org/10.3390/math13020242">Extensions of Riordan Arrays and Their Applications</a>, Mathematics (2025) Vol. 13, No. 2, 242. See p. 8.
%F A321511 a(n) = A005130(n) - n!
%t A321511 a[n_] := Product[(3 k + 1)!/(n + k)!, {k, 0, n-1}] - n!; a /@ Range[0, 17] (* _Giovanni Resta_, Nov 20 2018 *)
%Y A321511 Cf. A005130.
%K A321511 nonn
%O A321511 0,5
%A A321511 _Wendy Appleby_, Nov 11 2018