|
|
A116837
|
|
Number of permutations of length n which avoid the patterns 3421, 4123, 4312; or avoid the patterns 2341, 3142, 3214.
|
|
0
|
|
|
1, 2, 6, 21, 73, 250, 853, 2911, 9938, 33931, 115849, 395534, 1350437, 4610679, 15741842, 53746011, 183500361, 626509422, 2139036965, 7303129015, 24934442130, 85131510491, 290657157705, 992365609838, 3388148123941
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: A(x) = -x*(x-1)^3/((x^2-x+1)*(2*x^2-4*x+1)).
|
|
MATHEMATICA
|
CoefficientList[Series[-(x - 1)^3/((x^2 - x + 1) (2 x^2 - 4 x + 1)), {x, 0, 30}], x] (* Wesley Ivan Hurt, Dec 28 2023 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|