A107762 -id:A107762 - cp's OEIS frontend

A107761 Number of permutations of (1,3,5,7,9,...,2n-1) where every adjacent pair in the permutation are coprime.

1, 2, 6, 24, 72, 480, 3600, 9600, 108000, 1270080, 4795200, 74088000, 768539520, 4759413120, 94182359040, 1893397524480, 11353661706240, 122634632171520, 3104438623534080, 23063946114908160, 664424069072117760

Offset: 1

Ray Chandler, following a suggestion of Leroy Quet, Jun 11 2005

nonn

Odd analog of A076220.

			For example, if n = 5, the permutation (5,3,7,9,1) is counted, but (5,3,9,1,7) is not counted because 3 and 9 are adjacent.

Cf. A076220, A086595, A102381, A107762, A107763.

With[{n=9}, per=Permutations[Range[1, 2 n -1, 2]]; Select[per, Times @@ Table[GCD @@Partition[ #, 2, 1][[i]], {i, n-1}]==1&]//Length] (Seidov)

a(1)-a(9) computed by Zak Seidov.

More terms from Max Alekseyev, Jun 11 2005

A107763 Number of ways to arrange the numbers (1,3,5,7,9,...,2n-1) in a circle such that every two adjacent numbers are relatively prime.

Original entry on oeis.org

1, 1, 2, 6, 12, 72, 480, 864, 9600, 108000, 312000, 4795200, 46293120, 241056000, 4759413120, 94182359040, 478511953920, 4873965022080, 122634632171520, 799554193966080, 23063946114908160, 664424069072117760, 3198456730188840960, 108184656752428032000, 2657146152621477888000, 22850984107452933734400, 863305241854715928576000, 15282315334192501724774400, 151673086024479840160972800

Offset: 1

Ray Chandler, Jun 11 2005

nonn

Odd analog of A086595.

Cf. A076220, A086595, A102381, A107761, A107762.

More terms from Max Alekseyev, Jun 11 2005

a(23)-a(29) from Max Alekseyev, Jul 08 2014

cp's OEIS Frontend

A107761 Number of permutations of (1,3,5,7,9,...,2n-1) where every adjacent pair in the permutation are coprime.

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Mathematica

Extensions