id:A057170 - OEIS Search Results

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2-enumeration of 2n X 2n half-turn symmetric alternating-sign matrices.

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1, 2, 12, 288, 26880, 10035200, 14836039680, 87734404251648, 2064716402685640704, 194361783607326689722368, 72958995691997968023051829248, 109548594452892660460226753134067712, 656593430123179564638165745256190909087744, 15741504841171021653720624575980053578961033101312 (list; graph; listen)

	OFFSET	`0,2`
	LINKS	`G. Kuperberg, Symmetry classes of alternating-sign matrices under one roof, arXiv math.CO/0008184 [Th. 3]`
	MAPLE	`A057170 := proc(n) local i, j, t1; t1 := 2^(n^2); for i to n do for j to n do if j-i mod 2 <> 0 then t1 := t1(2j - 2i + 1)/(2j - 2*i) end if end do end do; t1 end proc;`
	CROSSREFS	`Sequence in context: A012754 A083568 A003121 this_sequence A008338 A000178 A108395` `Adjacent sequences: A057167 A057168 A057169 this_sequence A057171 A057172 A057173`
	KEYWORD	`nonn,easy`
	AUTHOR	`njas, Feb 04 2001`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

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