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A353965
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Number of tilings of a 3 X n rectangle using 2 X 2 and 1 X 1 tiles and right trominoes.
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2
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1, 1, 13, 47, 259, 1189, 5877, 28167, 136723, 660173, 3194613, 15445007, 74699811, 361230229, 1746933205, 8448061879, 40854753875, 197572345789, 955455626773, 4620559362303, 22344915889827, 108059470995013, 522573007884725, 2527150465444071, 12221238828079379
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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G.f.: (1 - 2*x + x^2) / (1 - 3*x - 9*x^2 + x^3 - 2*x^4).
a(n) = 3*a(n-1) + 9*a(n-2) - a(n-3) + 2*a(n-4).
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EXAMPLE
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a(2) = 13:
v h,v h=v h,v
___ ___ ___ ___ ___
| | | |_| | _| | _| |_|_| mirroring included
|___| |___| |_| | |_|_| |_|_| h: horizontal, v: vertical
|_|_| |_|_| |___| |_|_| |_|_|
2 + 4 + 2 + 4 + 1 = 13
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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