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
Keywords
Links
- Andrew Howroyd, Table of n, a(n) for n = 6..500
Programs
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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
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)
Extensions
Terms a(17) and beyond from Andrew Howroyd, May 05 2020