A144045 Number of paths of a chess Rook in a cube, from (1,1,1) to (n,n,n), where the rook may move in steps that are multiples of (1,0,0), (0,0,1), or (0,0,1).

1, 6, 222, 9918, 486924, 25267236, 1359631776, 75059524392, 4223303759148, 241144782230124, 13930829740017132, 812470444305924300, 47760356825349969600, 2826309951801018736800, 168207011284961649886800, 10060178088232285063542768, 604273284101165691102038556

Offset

1,2

Links

Table of n, a(n) for n=1..17.

Alin Bostan, Calcul Formel pour la Combinatoire des Marches [The text is in English], Habilitation à Diriger des Recherches, Laboratoire d’Informatique de Paris Nord, Université Paris 13, December 2017.

M. Kauers and D. Zeilberger, The Computational Challenge of Enumerating High-Dimensional Rook Walks, arXiv:1011.4671 [math.CO], 2010.

Formula

a(n) satisfies the recurrence relation a(1) = 1; a(2) = 6; a(3) = 222; a(4) = 9918; a(n) = ((-121 n^3 + 575n^2 - 872n + 412)a(n - 1) + (-475n^3 + 4887n^2 - 16202n + 17448)a(n - 2) + (1746n^3 - 19818n^2 + 75060n - 94896)a(n - 3) + (-1152n^3 + 16128n^2 - 74880n + 115200)a(n - 4))/(-(2n^3 - 8n^2 + 10n - 4)), n>= 5.

G.f.: 1+int(6*hypergeom([1/3, 2/3],[2],27*x*(3*x-2)/(4*x-1)^3)/((4*x-1)*(64*x-1)),x). [Mark van Hoeij, Dec 10 2009]

Asymptotics: a(n) ~ 9*sqrt(3)/(40*Pi*n)*64^(n-1). - Frederic Chyzak, 2010

Example

a(2)=6 because there are 6 Rook paths from (1,1,1) to (2,2,2).
G.f. = x + 6*x^2 + 222*x^3 + 9918*x^4 + 486924*x^5 + 25267236*x^6 + ...

Crossrefs

Cf. A051708.

Row d=3 of A181731.

Sequence in context: A331477 A144658 A203637 * A355669 A061610 A054324

Adjacent sequences: A144042 A144043 A144044 * A144046 A144047 A144048

Keyword

nonn

Author

Martin J. Erickson (erickson(AT)truman.edu), Sep 08 2008

Status

approved