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A159728 Number of permutations of 4 indistinguishable copies of 1..n arranged in a circle with exactly 2 local maxima. 6
36, 2610, 129800, 5748750, 241987500, 9885006250, 395426250000, 15570077343750, 605504070312500, 23311913238281250, 890091272109375000, 33749294301074218750, 1272088786561523437500, 47703329503967285156250, 1780924301526757812500000, 66228122463283630371093750 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
LINKS
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
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, Apr 20 2009
EXTENSIONS
Terms a(8) and beyond from Andrew Howroyd, May 09 2020
STATUS
approved

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Last modified March 29 06:44 EDT 2024. Contains 371265 sequences. (Running on oeis4.)