|
|
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
|
|
|
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
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|