

A070862


Number of path covers of an n X n grid.


1




OFFSET

1,2


COMMENTS

A path cover is set of disjoint paths such that each node of the graph belongs to exactly one of these. A Hamiltonian path is a special path cover consisting of a single path. Paths of length zero (i.e. single nodes) are permitted.


LINKS

Table of n, a(n) for n=1..9.


EXAMPLE

a(1) = 1 as there is only the trivial cover by a single path of length 0
a(2) = 15 = 1 (all length 0) + 4 (2x0, 1x1) + 2 (2x1) + 4 (1x2, 1x0) + 4 (1x3)


CROSSREFS

Sequence in context: A069450 A205346 A208868 * A077730 A110103 A232305
Adjacent sequences: A070859 A070860 A070861 * A070863 A070864 A070865


KEYWORD

nonn


AUTHOR

Andre Poenitz (poenitz(AT)htwm.de), Nov 26 2003


STATUS

approved



