OFFSET
1,5
COMMENTS
This 3-D array is represented as a triangle in which row m shows the square matrix A(m;r,s) (1 <= r <= m, 1 <= s <= m) read across rows.
The array is symmetrical in the sense that f(m;r,s) = f(m;s,r).
LINKS
John Riordan and Paul R. Stein, Arrangements on chessboards, Journal of Combinatorial Theory, Series A 12.1 (1972): 72-80. See A(m;r,s) in Section 2, Eq. (9).
EXAMPLE
The square slices for m = 1,2,3,4,5,6,7 are:
m=1:
[[1]],
m=2:
[[0, 1],
[1, 2]],
m=3:
[[0, 0, 1],
[0, 4, 6],
[1, 6, 6]],
m=4:
[[0, 0, 0, 1],
[0, 1, 12, 14],
[0, 12, 45, 36],
[1, 14, 36, 24]],
m=5:
[[0, 0, 0, 0, 1],
[0, 0, 6, 32, 30],
[0, 6, 90, 228, 150],
[0, 32, 228, 432, 240],
[1, 30, 150, 240, 120]],
m=6:
[[0, 0, 0, 0, 0, 1],
[0, 0, 1, 24, 80, 62],
[0, 1, 78, 522, 975, 540],
[0, 24, 522, 2248, 3300, 1560],
[0, 80, 975, 3300, 4200, 1800],
[1, 62, 540, 1560, 1800, 720]],
m=7:
[[0, 0, 0, 0, 0, 0, 1],
[0, 0, 0, 8, 80, 192, 126],
[0, 0, 36, 624, 2595, 3798, 1806],
[0, 8, 624, 5776, 17300, 20520, 8400],
[0, 80, 2595, 17300, 43000, 45000, 16800],
[0, 192, 3798, 20520, 45000, 43200, 15120],
[1, 126, 1806, 8400, 16800, 15120, 5040]],
MAPLE
f:=(m, r, s) -> add( add( (-1)^(i+j+r+s)*binomial(r, i)*binomial(s, j)*binomial(i*j, m), j=0..s), i=0..r);
sq:=m -> [seq([seq(f(m, r, s), r=1..m)], s=1..m)];
for m from 1 to 8 do lprint(sq(m)); od:
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
N. J. A. Sloane, Jun 06 2020
STATUS
approved