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A220770 Number of tilings of a 4 X n rectangle using integer sided rectangular tiles of equal area. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A065891 A321173 A147328 * A191527 A226106 A026566

Adjacent sequences:  A220767 A220768 A220769 * A220771 A220772 A220773

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Dec 19 2012

STATUS

approved

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Last modified August 2 09:22 EDT 2021. Contains 346422 sequences. (Running on oeis4.)