A005777 Rook polynomials.
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
Keywords
References
- N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Links
- Earl Glen Whitehead, Jr., Four-discordant permutations, J. Austral. Math. Soc. Ser. A 28 (1979), no. 3, 369-377.
Crossrefs
A diagonal of A259985.
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
Extensions
More terms from Sean A. Irvine, Aug 27 2016