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A215252 Number of indecomposable permutations sortable using two parallel stacks. 4
0, 1, 1, 3, 12, 56, 289, 1602, 9367, 57075, 359346, 2323416, 15356446, 103389175, 707107627, 4901988047, 34384943850, 243694702311, 1742953208739, 12567593026554, 91280392585747, 667341975412356, 4907899368783645, 36289929612761691, 269660272111724536, 2012845416966620068, 15087243969226496324, 113521159338891300347, 857211201390859034536 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Suggested by Peter Doyle in an email message, Sep 04 2012

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 0..100

FORMULA

INVERTi transform of A216040.

CROSSREFS

Cf. A003319, A216040, A182216, A215257.

Sequence in context: A301418 A224922 A303925 * A284712 A284713 A180256

Adjacent sequences:  A215249 A215250 A215251 * A215253 A215254 A215255

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 07 2012. a(0)=0 added by N. J. A. Sloane, Sep 12 2012

STATUS

approved

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Last modified February 28 09:52 EST 2020. Contains 332323 sequences. (Running on oeis4.)