

A287378


Triangle read by rows: T(n,m) is the number of inequivalent n X m matrices under action of the Klein group, with oneeighth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's and 8's (ordered occurrences rounded up/down if n*m != 0 mod 8).


8



1, 1, 1, 1, 1, 1, 1, 1, 1, 45360, 1, 1, 10080, 7484544, 20432442240, 1, 1, 226800, 2554075440, 29331862801920, 577185873264000000
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,10


COMMENTS

Computed using Polya's enumeration theorem for coloring.


LINKS



FORMULA

g(x1,x2,x3,x4,x5,x6,x7,x8) = (y1^(m*n) + 3*y2^(m*n/2))/4 for even n and m;
(y1^(m*n) + y1^n*y2^((m*nm)/2) + 2*y2^(m*n/2))/4 for odd n and even m;
(y1^(m*n) + y1^m*y2^((m*nn)/2) + 2*y2^(m*n/2))/4 for even n and odd m;
(y1^(m*n) + y1^n*y2^((m*nn)/2) + y1^m*y2^((m*nm)/2) + y1*y2^((m*n1)/2))/4 for odd n and m, where the coefficients y1 and y2 correspond to y1 = Sum_{i=1..8} x_i and y2 = Sum_{i=1..8} x_i^2. Occurrences of numbers are ceiling(m*n/8) for the first k numbers and floor(m*n/8) for the last (8k) numbers, if m*n = k mod 8.


EXAMPLE

For n = 4 and m = 2, the T(4,2) = 10080 solutions are colorings of 4 X 2 matrices in 8 colors inequivalent under the action of the Klein group with exactly 1 occurrence of each color (coefficient of x1^1, x2^1, x3^1, x4^1, x5^1, x6^1, x7^1, x8^1).
Triangle begins:
=================================================================
n\m  0 1 2 3 4 5

0  1
1  1 1
2  1 1 1
3  1 1 1 45360
4  1 1 10080 7484544 20432442240
5  1 1 226800 2554075440 29331862801920 577185873264000000


CROSSREFS



KEYWORD



AUTHOR



STATUS

approved



