OFFSET
3,2
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J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)
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 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Vladeta Jovovic, Vladimir Baltic, Jan 23 2003
a(21)-a(23) from Vaclav Kotesovec, Oct 10 2017
STATUS
approved