A151579 Number of permutations of 1..n arranged in a circle with exactly 6 adjacent element pairs in decreasing order.

0, 7, 960, 38637, 882340, 14413894, 188690976, 2112659718, 21078701112, 192648942945, 1644431982848, 13295963811083, 102911255502876, 768689550213368, 5575887557096640, 39473882067826332, 273820542615005232, 1867156445048432043, 12548621876834960064

Offset

6,2

Links

Andrew Howroyd, Table of n, a(n) for n = 6..500

Formula

From Andrew Howroyd, May 05 2020: (Start)

a(n) = n*A000514(n-1).

a(n) = n*(6^(n-1) - n*5^(n-1) + binomial(n,2)*4^(n-1) - binomial(n,3)*3^(n-1) + binomial(n,4)*2^(n-1) - binomial(n,5)). (End)

Prog

(PARI) a(n) = {n*(6^(n-1) - n*5^(n-1) + binomial(n, 2)*4^(n-1) - binomial(n, 3)*3^(n-1) + binomial(n, 4)*2^(n-1) - binomial(n, 5))} \\ Andrew Howroyd, May 05 2020

Crossrefs

Column k=6 of A334218.

Cf. A000514.

Sequence in context: A068728 A028990 A304396 * A024098 A172918 A286913

Adjacent sequences: A151576 A151577 A151578 * A151580 A151581 A151582

Keyword

nonn

Author

R. H. Hardin, May 21 2009

Extensions

Terms a(17) and beyond from Andrew Howroyd, May 05 2020

Status

approved