id:A059475 - OEIS Search Results

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Number of 2n X 2n half-turn symmetric alternating-sign matrices (HTSASM's).

+0
3

1, 2, 10, 140, 5544, 622908, 198846076, 180473355920, 465904151957920, 3422048076740462480, 71525763221287897903500, 4254840960508487045451825000, 720428791920558617462950575000000, 347230535542092373572967034254050000000 (list; graph; listen)

	OFFSET	`0,2`
	LINKS	`J. de Gier, Loops, matchings and alternating-sign matrices` `G. Kuperberg, Symmetry classes of alternating-sign matrices under one roof, arXiv math.CO/0008184`
	FORMULA	`A005130(n)*A006366(n).`
	CROSSREFS	`Even-numbered terms of A005158.` `Sequence in context: A087417 A091990 A014228 this_sequence A003046 A137884 A057565` `Adjacent sequences: A059472 A059473 A059474 this_sequence A059476 A059477 A059478`
	KEYWORD	`nonn`
	AUTHOR	`njas, Feb 04 2001`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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