OFFSET
1,7
COMMENTS
Equivalently, the number of rook tours on an n X m lattice.
2*T(n,m) is divisible by (n-1)!*(m-1)!. - Andrew Howroyd, Feb 08 2021
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..96
Eric Weisstein's World of Mathematics, Hamiltonian Cycle
Eric Weisstein's World of Mathematics, Rook Graph
FORMULA
EXAMPLE
Array begins:
=============================================================
n\m | 1 2 3 4 5
----+--------------------------------------------------------
1 | 0 0 1 3 12 ...
2 | 0 1 3 30 480 ...
3 | 1 3 48 1566 126120 ...
4 | 3 30 1566 284112 122330880 ...
5 | 12 480 126120 122330880 335750676480 ...
6 | 60 12000 18153720 112777827840 2190773906150400 ...
7 | 360 430920 4357332000 ...
...
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Andrew Howroyd, Feb 29 2016
STATUS
approved