A059487 Number of 2-enumeration of 4n X 4n quarter-turn symmetric alternating-sign matrices.

1, 2, 80, 53760, 590413824, 104981650735104, 300931721514121691136, 13874404129378738693891686400, 10274196157891080769280680484929536000, 122089077024940067215877965611538507917950976000, 23266604385482749027479729551862778584550130343015874560000

Offset

0,2

Links

Table of n, a(n) for n=0..10.

G. Kuperberg, Symmetry classes of alternating-sign matrices under one roof, arXiv:math/0008184 [math.CO], 2000-2001; [Th. 3].

Maple

A059487 := proc(n) local i, j, t1; t1 := (-1)^(n*(n-1)/2)*2^(2*n^2-n); for i to n do for j to n do t1 := t1*(4*j - 4*i + 1)/(j - i + n); end do end do; t1 end proc;

Mathematica

a[n_] := Module[{t1 = (-1)^(n*(n - 1)/2)*2^(2*n^2 - n)}, Do[t1 = t1*(4*j - 4*i + 1)/(j - i + n), {j, n}, {i, n}]; t1];
Array[a, 11, 0] (* Jean-François Alcover, Nov 28 2017, from Maple *)

Crossrefs

Sequence in context: A351854 A210277 A008563 * A156932 A291331 A369468

Adjacent sequences: A059484 A059485 A059486 * A059488 A059489 A059490

Keyword

nonn,easy

Author

N. J. A. Sloane, Feb 04 2001

Status

approved