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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
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 A191602 A145157
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 March 18 22:50 EDT 2024. Contains 370951 sequences. (Running on oeis4.)