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A001889
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Hit polynomials.
(Formerly M3345 N1346)
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1
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1, 4, 8, 38, 209, 1400, 10849, 95516, 938441, 10179149, 120748974, 1554688240, 21588485677, 321561688748, 5113709884902, 86469576394028, 1549114961438599, 29309613834899864, 583986501706555597, 12222118836543561940, 268060239251978779839, 6148136982942476816891
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OFFSET
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2,2
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REFERENCES
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J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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).
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LINKS
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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N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)
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CROSSREFS
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Third column of A080061.
Cf. A001883-A001891.
Sequence in context: A225824 A032317 A032226 * A032138 A032151 A032042
Adjacent sequences: A001886 A001887 A001888 * A001890 A001891 A001892
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane
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EXTENSIONS
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More terms from Vladeta Jovovic, Vladimir Baltic, Jan 23 2003
a(21)-a(23) from Vaclav Kotesovec, Oct 10 2017
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STATUS
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approved
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