A219971 Number of tilings of a 7 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles.

1, 0, 3, 13, 31, 170, 804, 2744, 12343, 55657, 214485, 923990, 4008013, 16241904, 68963484, 293830787, 1216393406, 5135225641, 21711233759, 90692128053, 381960417890, 1609647053073, 6749229887672, 28396742081001, 119506154362773, 501879008939056

Offset: 0

Author

Alois P. Heinz, Dec 02 2012

Keywords

• nonn

Examples

			a(2) = 3, because there are 3 tilings of a 7 X 2 rectangle using straight (3 X 1) trominoes and 2 X 2 tiles:
._._.   .___.   .___.
| | |   |   |   |   |
| | |   |___|   |___|
|_|_|   | | |   |   |
|   |   | | |   |___|
|___|   |_|_|   | | |
|   |   |   |   | | |
|___|   |___|   |_|_|
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..500

Crossrefs

Column k=7 of A219967.