id:A137729 - OEIS Search Results

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Number of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations).

+0
6

1, 2, 16, 318, 11352, 623760, 48648960, 5108105520, 694702028160, 118794043549440, 24946749109094400, 6311527524161798400, 1893458257242791500800, 664603848292138865510400, 269829162406607158901145600 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`a(n) = ((2n)!/2^n + n!) / (2n).`
	CROSSREFS	`Cf. A114938, A137730, A137737, A137749.` `Sequence in context: A112722 A009250 A140051 this_sequence A009100 A009109 A012610` `Adjacent sequences: A137726 A137727 A137728 this_sequence A137730 A137731 A137732`
	KEYWORD	`nonn`
	AUTHOR	`Max Alekseyev (maxal(AT)cs.ucsd.edu), Feb 09, 2008`

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Last modified December 3 01:16 EST 2008. Contains 151161 sequences.

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