A001890 Hit polynomials.

1, 10, 34, 206, 1351, 10543, 92708, 912884, 9917445, 117838808, 1519483258, 21128310078, 315093762147, 5016410089130, 84909414423784, 1522548805068310, 28830824064870329, 574880701875755325, 12039866150973004846, 264230694283295736788, 6063848537910027941323

Offset: 3

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• J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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• N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)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

Fourth column of A080061.

Cf. A001883-A001891.

Programs

Mathematica

(* Program not suitable to compute more than a dozen terms *)
M[n_] := Table[If[0 <= i - j <= 2, x, 1], {i, 1, n}, {j, 1, n}];
a[n_] := Coefficient[Permanent[M[n]], x, 3];
Table[an = a[n]; Print[n, " ", an]; an, {n, 3, 15}] (* Jean-François Alcover, Jan 12 2018 *)

Extensions

More terms from Vladeta Jovovic, Vladimir Baltic, Jan 23 2003

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