A001884 Hit polynomials.

1, 0, 1, 2, 20, 104, 775, 6140, 55427, 553802, 6087992, 72994152, 948103477, 13262133736, 198769630061, 3177862894922, 53984653965996, 971068821144112, 18438722595913195, 368558842844143268, 7735520783692157215, 170095060428041137778, 3910332719957508452016, 93806427360751009531632

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

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• J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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

• N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)

Crossrefs

Second column of A080018.

Cf. A001883-A001891.

Extensions

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

a(21)-a(24) from Vaclav Kotesovec, Oct 10 2017