A001885 Hit polynomials. (Formerly M0384 N0144)

2, 2, 10, 28, 207, 1288, 10366, 91296, 903037, 9832848, 117032570, 1510932116, 21028774738, 313832463386, 4999133311044, 84655108256252, 1518546437350265, 28763765236019284, 573689119174695326, 12017485839703597024, 263787711208968183879, 6054632852404055079936

Offset

2,1

References

J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963. (See A001883).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=2..23.

N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)

Crossrefs

Third column of A080018.

Cf. A001883-A001891.

Sequence in context: A102345 A151364 A200949 * A300641 A078433 A059494

Adjacent sequences: A001882 A001883 A001884 * A001886 A001887 A001888

Keyword

nonn

Author

N. J. A. Sloane

Extensions

More terms from Vladeta Jovovic and Vladimir Baltic, Jan 20 2003

a(21)-a(23) from Vaclav Kotesovec, Oct 10 2017

Status

approved