A220770 Number of tilings of a 4 X n rectangle using integer-sided rectangular tiles of equal area.

1, 3, 9, 20, 49, 115, 343, 850, 2401, 6698, 18677, 52383, 148417, 418280, 1184717, 3357537, 9518235, 27001128, 76637532, 217530615, 617624137, 1753811531, 4980521844, 14144892243, 40174244540, 114105904403, 324101321331, 920579535645, 2614852152957

Offset

0,2

Comments

a(n+1)/a(n) tends to r = (1+sqrt(29)+sqrt(2*(7+sqrt(29))))/4 = 2.840536194094952533051131..., where r is the largest root of x^4-x^3-5*x^2-x+1. - Vaclav Kotesovec, Dec 21 2012

Links

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Example

a(2) = 9:
.___. .___. .___. .___. .___. .___. .___. .___. .___.
|   | | | | |   | |___| | | | |___| |___| | | | |_|_|
|   | | | | |___| |___| |_|_| | | | |___| |_|_| |_|_|
|   | | | | |   | |___| |___| |_|_| | | | | | | |_|_|
|___| |_|_| |___| |___| |___| |___| |_|_| |_|_| |_|_|

Crossrefs

Column k=4 of A220777.

Sequence in context: A321173 A147328 A364914 * A191527 A226106 A026566

Adjacent sequences: A220767 A220768 A220769 * A220771 A220772 A220773

Keyword

nonn

Author

Alois P. Heinz, Dec 19 2012

Status

approved