A005777 Rook polynomials. (Formerly M3544)

1, 4, 18, 96, 265, 672, 1617, 3776, 8577, 19080, 41745, 90048, 191945, 404992, 846945, 1757440, 3621697, 7417800, 15109313, 30623520, 61788489, 124158496, 248549937, 495852480, 986076225, 1955203016, 3866245425, 7625813888, 15005718153

Offset

1,2

References

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..29.

Earl Glen Whitehead, Jr., Four-discordant permutations, J. Austral. Math. Soc. Ser. A 28 (1979), no. 3, 369-377.

Formula

Conjecture: G.f.: x + 4*x^2 - 15*x^3 + x^3*((33 - 69*x + 16*x^2 - 14*x^3 + 82*x^4 - 8*x^5 - 20*x^6 - 38*x^7 + 9*x^8 + 9*x^9 + 8*x^10) / ((1 - x)^2 * (1 - x - x^2 - x^3)^3)). - Vaclav Kotesovec, Aug 27 2016

Crossrefs

A diagonal of A259985.

Sequence in context: A370344 A081103 A243325 * A180567 A152392 A001563

Adjacent sequences: A005774 A005775 A005776 * A005778 A005779 A005780

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

More terms from Sean A. Irvine, Aug 27 2016

Status

approved