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

Offset: 1

Author

Giovanni Resta, Mar 28 2006

Keywords

• nonn

Comments

Sequence suggested by Leroy Quet on the SeqFan mailing list.

Examples

			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.