A159728 Number of permutations of 4 indistinguishable copies of 1..n arranged in a circle with exactly 2 local maxima.

36, 2610, 129800, 5748750, 241987500, 9885006250, 395426250000, 15570077343750, 605504070312500, 23311913238281250, 890091272109375000, 33749294301074218750, 1272088786561523437500, 47703329503967285156250, 1780924301526757812500000, 66228122463283630371093750

Offset

2,1

Links

Andrew Howroyd, Table of n, a(n) for n = 2..200

Index entries for linear recurrences with constant coefficients, signature (85,-2350,23750,-100625,153125).

Formula

a(n) = 2*n*(121*35^(n-2) + 8*5^(n-2) - 24*n*5^(n-2))/9. - Andrew Howroyd, May 10 2020

Prog

(PARI) a(n) = {2*n*(121*35^(n-2) + 8*5^(n-2) - 24*n*5^(n-2))/9} \\ Andrew Howroyd, May 10 2020
(PARI) Vec(2*x^2*(3 + 5*x)*(6 - 85*x - 1100*x^2 + 875*x^3) / ((1 - 5*x)^3*(1 - 35*x)^2) + O(x^40)) \\ Colin Barker, Jul 16 2020

Crossrefs

Column k=4 of A334772.

Cf. A159716.

Sequence in context: A120466 A202633 A198639 * A268365 A004706 A061844

Adjacent sequences: A159725 A159726 A159727 * A159729 A159730 A159731

Keyword

nonn,easy

Author

R. H. Hardin, Apr 20 2009

Extensions

Terms a(8) and beyond from Andrew Howroyd, May 09 2020

Status

approved