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 A001890 Hit polynomials. (Formerly M4696 N2005) 2
 1, 10, 34, 206, 1351, 10543, 92708, 912884, 9917445, 117838808, 1519483258, 21128310078, 315093762147, 5016410089130, 84909414423784, 1522548805068310, 28830824064870329, 574880701875755325, 12039866150973004846, 264230694283295736788, 6063848537910027941323 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,2 REFERENCES J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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 LINKS N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963) MATHEMATICA (* Program not suitable to compute more than a dozen terms *) M[n_] :=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 Fourth column of A080061. Cf. A001883-A001891. Sequence in context: A264671 A341300 A232902 * A221810 A219591 A272365 Adjacent sequences:  A001887 A001888 A001889 * A001891 A001892 A001893 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

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Last modified September 27 18:31 EDT 2021. Contains 347694 sequences. (Running on oeis4.)