A057629 Number of alternating sign 2n X 2n matrices invariant under flips in both diagonals.

2, 8, 52, 568, 10436, 323144, 16866856, 1484714416, 220426128584

Offset

1,1

Links

Table of n, a(n) for n=1..9.

D. P. Robbins, Symmetry classes of alternating sign matrices, arXiv:math/0008045 [math.CO], 2000.

Formula

a(n) = A005162(2*n).

Crossrefs

Even numbered terms of A005162.

Cf. A059475.

Sequence in context: A191552 A154828 A349012 * A191507 A378400 A191602

Adjacent sequences: A057626 A057627 A057628 * A057630 A057631 A057632

Keyword

nonn,more,nice

Author

N. J. A. Sloane, Oct 10 2000

Extensions

a(8)-a(9) from A005162(2*n) by Jinyuan Wang, Mar 03 2020

Status

approved