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A005164
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Number of alternating sign 2n+1 X 2n+1 matrices invariant under all symmetries of the square.
(Formerly M1271)
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3
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1, 1, 1, 2, 4, 13, 46, 248, 1516, 13654, 142873, 2156888, 38456356, 974936056, 29540545024, 1259111024288, 64726478396896, 4641989615977216, 404396533544588344, 48825344233129714772, 7202552030561982627472, 1464587581921220811285325, 365627222082497915618219716, 125253905685915522767942493032, 52893528399758443649956432899616
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OFFSET
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0,4
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REFERENCES
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M. Bousquet-Mélou and L. Habsieger, Sur les matrices à signes alternants, Séries Formelles et Combinatoire Algébrique, 4th colloquium, 15-19 Juin 1992, Montréal, Université du Québec à Montréal, pp. 19-32.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. P. Stanley, A baker's dozen of conjectures concerning plane partitions, pp. 285-293 of "Combinatoire Enumerative (Montreal 1985)", Lect. Notes Math. 1234, 1986.
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LINKS
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FORMULA
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Hagendorf and Liénardy give a (conjectured) formula in terms of multiple contour integrals. - Jean Liénardy, Aug 15 2020
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CROSSREFS
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KEYWORD
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nonn,nice,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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