OFFSET
0,24
LINKS
Alois P. Heinz, Antidiagonals n = 0..20, flattened
S. Butler, J. Ekstrand, S. Osborne, TETRIS Tiling, AMS Spring Central Sectional, Iowa State University, April 27-28 2013
R. S. Harris, Counting Polyomino Tilings
Wikipedia, Tetris
Wikipedia, Tetromino
FORMULA
A(n,k) = 0 <=> n*k mod 4 > 0.
EXAMPLE
A(4,2) = A(2,4) = 4:
._______. ._______. ._______. ._______.
| | | |_______| | |___. | | .___| |
|___|___| |_______| |_____|_| |_|_____|.
Square array A(n,k) begins:
1, 1, 1, 1, 1, 1, 1, 1, 1, ...
1, 0, 0, 0, 1, 0, 0, 0, 1, ...
1, 0, 1, 0, 4, 0, 9, 0, 25, ...
1, 0, 0, 0, 23, 0, 0, 0, 997, ...
1, 1, 4, 23, 117, 454, 2003, 9157, 40899, ...
1, 0, 0, 0, 454, 0, 0, 0, 800290, ...
1, 0, 9, 0, 2003, 0, 178939, 0, 22483347, ...
1, 0, 0, 0, 9157, 0, 0, 0, 657253434, ...
1, 1, 25, 997, 40899, 800290, 22483347, 657253434, 19077209438, ...
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Alois P. Heinz, Nov 29 2013
STATUS
approved