|
|
A233266
|
|
Number of tilings of a 4 X n rectangle using tetrominoes of shapes L, T, Z.
|
|
7
|
|
|
1, 0, 2, 10, 24, 70, 276, 820, 2616, 8702, 27902, 89500, 291050, 939222, 3029950, 9798606, 31657182, 102237766, 330356240, 1067310022, 3447911968, 11139391996, 35988377472, 116265759012, 375619824338, 1213515477460, 3920484872552, 12665878390278
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (x^8 -4*x^7 +3*x^6 -2*x^5 -2*x^4 -2*x^3 +2*x^2 +2*x -1) / (-2*x^14 +8*x^13 -10*x^12 +16*x^11 -4*x^10 +20*x^9 -13*x^8 +4*x^7 +15*x^6 -28*x^5 -6*x^4 +4*x^3 +4*x^2 +2*x -1).
|
|
EXAMPLE
|
a(3) = 10:
._____. ._____. ._____. ._____. ._____.
| |_. | | ._| | | .___| |___. | | .___|
|_. | | | | ._| |_| | | | | |_| |_| ._|
| |_|_| |_|_| | | ._| | | |_. | |___| |
|_____| |_____| |_|___| |___|_| |_____|
._____. ._____. ._____. ._____. ._____.
| ._| | | |_. | |_. ._| |_. ._| |___. |
| |_. | | ._| | | |_| | | |_| | |_. |_|
|_| |_| |_| |_| | |_. | | ._| | | |___|
|_____| |_____| |___|_| |_|___| |_____|.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|