A117542 - OEIS

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A117542

Number of permutations P of 1..n such that in P and in the inverse of P, every pair of adjacent numbers and the first and last number, are relatively prime.

1, 2, 6, 8, 36, 16, 127, 320, 581, 1564, 13565, 13760, 149186, 773727, 540538 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,2`
	COMMENTS	`Sequence suggested by Leroy Quet on the SeqFan mailing list.`
	LINKS	`Table of n, a(n) for n=1..15.`
	EXAMPLE	`a(4)=8, since the 8 permutations (1,2,3,4), (1,4,3,2), (2,1,4,3), (2,3,4,1), (4,1,2,3), (3,2,1,4), (3,4,1,2), (4,3,2,1) satisfy the property.`
	CROSSREFS	`Cf. A076220, A117541.` `Sequence in context: A019199 A094678 A076507 * A045653 A152158 A095239` `Adjacent sequences: A117539 A117540 A117541 * A117543 A117544 A117545`
	KEYWORD	`nonn`
	AUTHOR	`Giovanni Resta, Mar 28 2006`
	STATUS	`approved`

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Last modified May 23 05:24 EDT 2013. Contains 225585 sequences.