

A335793


Number of hare popstack sortable Cayley permutations.


0




OFFSET

0,3


COMMENTS

Also, the set of Cayley permutations avoiding 231, 312, and 2121.


LINKS



FORMULA

G.f.: (1  4*x + 4*x^2  2*x^3) / (1  5*x + 6*x^2  4*x^3).
a(n) = 5*a(n1)  6*a(n2) + 4*a(n3) for n>3.
(End)


CROSSREFS



KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



