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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..7.

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

FORMULA

a(n) = A005162(2n).

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,nice,more

AUTHOR

N. J. A. Sloane, Oct 10 2000

STATUS

approved

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Last modified February 22 09:22 EST 2020. Contains 332133 sequences. (Running on oeis4.)