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A057629 Number of alternating sign 2n X 2n matrices invariant under flips in both diagonals. 0
2, 8, 52, 568, 10436, 323144, 16866856, 1484714416, 220426128584 (list; graph; refs; listen; history; text; internal format)
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: A151879 A191552 A154828 * A191507 A191602 A145157

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

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Last modified April 14 15:18 EDT 2021. Contains 342949 sequences. (Running on oeis4.)