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A233191 Number of tilings of a 4 X n rectangle using L and T tetrominoes. 7
1, 0, 2, 4, 12, 16, 76, 128, 386, 832, 2368, 5024, 13946, 31680, 82632, 193696, 498174, 1182464, 2993384, 7213648, 18061074, 43832960, 109163384, 266217472, 660116398, 1615451648, 3995295112, 9796774896, 24189684402, 59396496000, 146494223160, 360026507808 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

Wikipedia, Tetromino

FORMULA

G.f.: (2*x^6+x^4+2*x^2-1) / (-8*x^12 -8*x^9 -18*x^8 +12*x^7 +4*x^6 -8*x^5 +5*x^4 +4*x^3 +4*x^2 -1).

EXAMPLE

a(3) = 4:

._____.  ._____.  ._____.  ._____.

|_. ._|  |_. ._|  | |_. |  | ._| |

| |_| |  | |_| |  | ._| |  | |_. |

| ._| |  | |_. |  |_| |_|  |_| |_|

|_|___|  |___|_|  |_____|  |_____|.

MAPLE

gf:= (2*x^6+x^4+2*x^2-1) / (-8*x^12 -8*x^9 -18*x^8

     +12*x^7 +4*x^6 -8*x^5 +5*x^4 +4*x^3 +4*x^2 -1):

a:= n-> coeff(series(gf, x, n+1), x, n):

seq(a(n), n=0..40);

CROSSREFS

Cf. A084480, A174248, A226322, A230031, A232497, A233139, A233266.

Sequence in context: A303819 A074646 A097001 * A192533 A085931 A125885

Adjacent sequences:  A233188 A233189 A233190 * A233192 A233193 A233194

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Dec 05 2013

STATUS

approved

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Last modified August 24 18:12 EDT 2019. Contains 326295 sequences. (Running on oeis4.)