

A193316


Number of basic forbidden patterns of length n of the map f(x)=4x(1x) on the unit interval.


0




OFFSET

1,4


COMMENTS

A permutation pi is a forbidden pattern if there is no x in [0,1] such that the values x,f(x),f(f(x)),...,f^{n1}(x) are in the same relative order as pi_1,pi_2,...,pi_n. A forbidden pattern is basic if it is minimally forbidden, that is, the patterns obtained by removing pi_1 or pi_n are not forbidden.
a(n) is also the number of basic forbidden patterns of length n of the tent map x > 112x in [0,1].


LINKS



EXAMPLE

a(3) = 1 because the only basic forbidden pattern of length 3 is 321.
a(4) = 5 because the basic forbidden patterns of length 4 are 1423, 2134, 2143, 3142, 4231.


CROSSREFS



KEYWORD

nonn,more


AUTHOR



STATUS

approved



