A138619 Number of permutations of length n which are contained in a pin sequence.

1, 2, 6, 24, 120, 664, 3596, 19004, 99596, 521420, 2731292, 14313052, 75016940, 393181820, 2060736460, 10800601788, 56607287052, 296685718140, 1554966533836, 8149773122044, 42713977098636, 223869280280316

Offset

1,2

Links

Table of n, a(n) for n=1..22.

F. Bassino, M. Bouvel, and D. Rossin, Enumeration of Pin-Permutations, The Electronic Journal of Combinatorics, Vol. 18, No. 1 (2011), P57. [Vincent Vatter, Sep 15 2009]

R. Brignall, N. Ruskuc and V. Vatter, Simple permutations: decidability and unavoidable substructures, Theoretical Computer Science 391 (2008), 150-163.

Formula

G.f.: (1-7*x+13*x^2-17*x^3+2*x^4-8*x^5+12*x^6+12*x^7-8*x^8) / (1-8*x+19*x^2-26*x^3+14*x^4-12*x^5-8*x^6+20*x^7-8*x^8). See Bassino, Bouvel, and Rossin. [Vincent Vatter, Sep 15 2009]

Example

a(5)=120 because all permutations of length 5 can be embedded into pin sequences.

Crossrefs

Sequence in context: A152336 A152343 A177529 * A189841 A189256 A152344

Adjacent sequences: A138616 A138617 A138618 * A138620 A138621 A138622

Keyword

nonn

Author

Vincent Vatter, May 14 2008

Extensions

Extended (using g.f.) by Vincent Vatter, Sep 15 2009

Status

approved