|
|
A141253
|
|
Number of permutations that lie in the cyclic closure of Av(132)--i.e., at least one cyclic rotation of the permutation avoids the pattern 132.
|
|
2
|
|
|
1, 2, 6, 24, 100, 408, 1631, 6440, 25263, 98790, 385803, 1506156, 5881057, 22974406, 89804910, 351279584, 1375035208, 5386203792, 21113167346, 82816267480, 325055630634, 1276635121388, 5016837177052, 19725798613152, 77601159558800
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
M. D. Atkinson, M. H. Albert, R. E. L. Aldred, H. P. van Ditmarsch, C. C. Handley, D. A. Holton, D. J. McCaughan, C. Monteith, Cyclically closed pattern classes of permutations, Australasian J. Combinatorics 38 (2007), 87-100.
|
|
FORMULA
|
G.f.: (1-4*x+4*x^2-4*x^3-(1-2*x)*sqrt(1-4*x))/(2*x*(1-x)^2*sqrt(1-4*x)).
a(n) = n(C(n) - C(n-1) - ... - C(1)), where C(n) denotes the n-th Catalan number.
D-finite with recurrence -3*(n+1)*(n-3)*a(n) +n*(17*n-43)*a(n-1) +2*(-11*n^2+35*n-30)*a(n-2) +4*(n-2)*(2*n-5)*a(n-3)=0. - R. J. Mathar, Aug 19 2022
D-finite with recurrence (n-1)*(n-3)*(n+1)*a(n) -n*(5*n^2-16*n+9)*a(n-1) +2*n*(n-1)*(2*n-3)*a(n-2)=0. - R. J. Mathar, Aug 19 2022
|
|
EXAMPLE
|
a(5)=100 because 100 permutations of length 5 have at least one cyclic rotation which avoids 132.
|
|
MATHEMATICA
|
Rest[CoefficientList[Series[(1-4*x+4*x^2-4*x^3-(1-2*x)*Sqrt[1-4*x]) / (2*x*(1-x)^2*Sqrt[1-4*x]), {x, 0, 20}], x]] (* Vaclav Kotesovec, Mar 20 2014 *)
|
|
PROG
|
(PARI) x='x+O('x^50); Vec((1-4*x+4*x^2-4*x^3-(1-2*x)*sqrt(1-4*x))/(2*x*(1-x)^2*sqrt(1-4*x))) \\ G. C. Greubel, Mar 21 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|