login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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 A235320 A152158

Adjacent sequences:  A117539 A117540 A117541 * A117543 A117544 A117545

KEYWORD

nonn

AUTHOR

Giovanni Resta, Mar 28 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 25 04:26 EDT 2019. Contains 322451 sequences. (Running on oeis4.)