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A059486 3-enumeration of 2n+1 X 2n+1 vertically symmetric alternating-sign matrices.

%I A059486 #23 Jan 17 2021 11:16:32
%S A059486 1,1,5,126,16038,10320453,33590259846,553104735325740,
%T A059486 46084184498427053436,19430969437346561065941390,
%U A059486 41463730793298298041665385308325,447814224393522724673729884056814834500,24479424309393636290695101063892553945412075000
%N A059486 3-enumeration of 2n+1 X 2n+1 vertically symmetric alternating-sign matrices.
%H A059486 Harry J. Smith, <a href="/A059486/b059486.txt">Table of n, a(n) for n = 0..53</a>
%H A059486 G. Kuperberg, <a href="https://arxiv.org/abs/math/0008184">Symmetry classes of alternating-sign matrices under one roof</a>, arXiv:math/0008184 [math.CO], 2000-2001. [Th. 3, but the formula there is incorrect]
%H A059486 J. Propp, <a href="http://www.dmtcs.org/pdfpapers/dmAA0103.pdf">The many faces of alternating-sign matrices</a>, Discrete Mathematics and Theoretical Computer Science Proceedings AA (DM-CCG), 2001, 43-58.
%F A059486 a(n) ~ exp(1/36) * Gamma(1/3)^(1/3) * 3^(n*(4*n + 1)/2 + 11/36) * n^(1/36) / (2^(2*n*(n+1) + 7/12) * A^(1/3) * Pi^(1/6)), where A is the Glaisher-Kinkelin constant A074962. - _Vaclav Kotesovec_, Feb 24 2019
%p A059486 A059486 := proc(n) local i, j, t1; t1 := 3^(2*n^2)/2^(2*n^2 + n); for i to 2*n + 1 do for j to 2*n + 1 do if i mod 2 <> 0 and j mod 2 = 0 then t1 := t1*(3*j - 3*i + 1)/(3*j - 3*i) end if end do end do; t1 end proc;
%p A059486 e(n)= { local(A); A=Vec((1 - (1 - 9*x + O(x^(2*n + 1)))^(1/3))/(3*x)); matdet(matrix(n, n, i, j, A[i+j]))/3^n; } { for (n = 0, 100, a=e(n); if (a > 10^(10^3 - 6), break); write("b059486.txt", n, " ", a); ) } # _Harry J. Smith_, Jun 27 2009
%t A059486 a[n_] := Module[{i, j, t1}, t1 = 3^(2*n^2)/2^(2*n^2 + n); For[i = 1, i <= 2*n + 1, i++, For[j = 1, j <= 2*n + 1, j++, If[Mod[i, 2] != 0 && Mod[j, 2] == 0, t1 = t1*(3*j - 3*i + 1)/(3*j - 3*i)]]]; t1];
%t A059486 Table[a[n], {n, 0, 12}] (* _Jean-François Alcover_, Nov 23 2017, translated from Maple *)
%t A059486 Table[3^(2*n^2)/2^(2*n^2 + n) * Product[(2 + 6*i - 6*j)/(3 + 6*i - 6*j), {i, 0, n}, {j, 1, n}], {n, 0, 15}] (* _Vaclav Kotesovec_, Feb 24 2019 *)
%o A059486 (PARI) a(n)=local(A); if(n<0,0,A=Vec((1-(1-9*x+O(x^(2*n+1)))^(1/3))/(3*x)); matdet(matrix(n,n,i,j,A[i+j]))/3^n)
%o A059486 (PARI) e(n)= { local(A); A=Vec((1 - (1 - 9*x + O(x^(2*n + 1)))^(1/3))/(3*x)); matdet(matrix(n, n, i, j, A[i+j]))/3^n; } { for (n = 0, 100, a=e(n); if (a > 10^(10^3 - 6), break); write("b059486.txt", n, " ", a); ) } \\ _Harry J. Smith_, Jun 27 2009
%Y A059486 Cf. A025748, A227379.
%K A059486 nonn,easy
%O A059486 0,3
%A A059486 _N. J. A. Sloane_, Feb 04 2001