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 A138176 #8 Sep 27 2024 05:44:44
%S A138176 1,-4,144,-43264,106832896,-2155963622400,354617391605760000,
%T A138176 -474686810341051524710400,5166329306435680284163452174336,
%U A138176 -456900249341808231214942590547243565056
%N A138176 Hankel transform of A138175.
%C A138176 When aerated, gives Hankel transform of A138175.
%H A138176 A. V. Razumov and Yu. G. Stroganov, <a href="https://arxiv.org/abs/math-ph/0312071">On refined enumerations of some symmetry classes of alternating sign matrices</a>, arXiv:math-ph/0312071, 2003.
%F A138176 sqrt(abs(a(n)))/2^n = A005156(n).
%F A138176 a(n) = (-1)^n*(Product_{k=1..n} (6*k-2)!*(2*k-1)!/((4*k-1)!*(4*k-2)!))^2.
%K A138176 easy,sign
%O A138176 0,2
%A A138176 _Paul Barry_, Mar 03 2008