A214611 Number of permutations of length n sortable by a pop stack followed by a queue and then by a stack.

1, 2, 6, 24, 120, 685, 4148, 25661, 159829, 997870

Offset

1,2

Links

Table of n, a(n) for n=1..10.

R. Smith and V. Vatter, A stack and a pop stack in series, The Australasian Journal of Combinatorics, Volume 58(1) (2014), pp. 157-171.

Example

There are only a(6)=685 permutations of length 6 that can be sorted by this machine; the machine can sort all shorter permutations.

Crossrefs

Cf. A033321.

Sequence in context: A152347 A228393 A177526 * A177528 A177527 A068200

Adjacent sequences: A214608 A214609 A214610 * A214612 A214613 A214614

Keyword

nonn,hard,more

Author

Vincent Vatter, Mar 06 2013

Status

approved