|
|
A116780
|
|
Number of permutations of length n which avoid the patterns 2341, 4123, 4132.
|
|
0
|
|
|
1, 2, 6, 21, 74, 249, 804, 2540, 7977, 25106, 79327, 251328, 797094, 2527977, 8014590, 25401277, 80494292, 255072244, 808301057, 2561517150, 8117640043, 25725562136, 81526606470, 258364283985, 818775016906, 2594754502777
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: A(x) = -{(2x^5-6x^4+10x^3-11x^2+5x-1)x}/{2x^6-8x^5+19x^4-27x^3+19x^2-7x+1}
|
|
MATHEMATICA
|
LinearRecurrence[{7, -19, 27, -19, 8, -2}, {1, 2, 6, 21, 74, 249}, 30] (* Harvey P. Dale, Aug 03 2017 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|