A134664 - OEIS

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A134664

Number of 3-stack sortable permutations on n letters.

1, 2, 6, 24, 114, 606, 3494, 21426, 137901, 922862, 6377818, 45281958, 328969075 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	EXAMPLE	`a(5) = 114 because all but the 6 permutations 23451, 24351, 32451, 34251, 42351, 43251 on 5 letters become 12345 after at most 3 passes through the stack sorter.`
	CROSSREFS	`Cf. A000139.` `Sequence in context: A152329 A192088 A054872 * A171448 A068199 A189846` `Adjacent sequences: A134661 A134662 A134663 * A134665 A134666 A134667`
	KEYWORD	`hard,nonn`
	AUTHOR	`Eric S Rowland (erowland(AT)math.rutgers.edu), Jan 25 2008`

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Last modified February 14 07:16 EST 2012. Contains 205589 sequences.