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A001888 Hit polynomials.
(Formerly M3573 N1449)
1
1, 1, 1, 4, 21, 122, 849, 6719, 59873, 593686, 6483027, 77309508, 999569969, 13927664613, 208044077633, 3316415176712, 56193522437465, 1008499234742158, 19110533105114433, 381290148293261075, 7989548583615385153, 175418232627066361514, 4027213499971769192903, 96489861550805864197512 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

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J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.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

Table of n, a(n) for n=1..24.

N. J. A. Sloane, Annotated copy of Riordan's Three-Ply Staircase paper (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)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 A080061.

Cf. A001883-A001891.

Sequence in context: A274969 A236525 A277292 * A103769 A003014 A108404

Adjacent sequences:  A001885 A001886 A001887 * A001889 A001890 A001891

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

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

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

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)