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A214611 Number of permutations of length n sortable by a pop stack followed by a queue and then by a stack. 1
1, 2, 6, 24, 120, 685, 4148, 25661, 159829, 997870 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 20 10:41 EDT 2019. Contains 328257 sequences. (Running on oeis4.)