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A068921
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Number of ways to tile a 2 X n room with 1x2 Tatami mats. At most 3 Tatami mats may meet at a point.
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9
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1, 1, 2, 3, 4, 6, 9, 13, 19, 28, 41, 60, 88, 129, 189, 277, 406, 595, 872, 1278, 1873, 2745, 4023, 5896, 8641, 12664, 18560, 27201, 39865, 58425, 85626, 125491, 183916, 269542, 395033, 578949, 848491, 1243524, 1822473, 2670964, 3914488, 5736961
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OFFSET
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0,3
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 0..1000
R. J. Mathar, Paving rectangular regions with rectangular tiles: Tatami and Non-Tatami Tilings, arXiv:1311.6135 [math.CO], 2013, Table 1.
Index entries for linear recurrences with constant coefficients, signature (1,0,1).
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FORMULA
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For n >= 3, a(n) = a(n-1) + a(n-3).
a(n) = A000930(n+1).
From Frank Ruskey, Jun 07 2009: (Start)
G.f.: (1+x^2)/(1-x-x^3).
a(n) = sum( binomial(n-2j+1,j), j=0..floor(n/2) ). (End)
G.f.: Q(0)*( 1+x^2 )/2, where Q(k) = 1 + 1/(1 - x*(4*k+1 + x^2)/( x*(4*k+3 + x^2) + 1/Q(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Sep 08 2013
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MATHEMATICA
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LinearRecurrence[{1, 0, 1}, {1, 1, 2}, 42] (* Robert G. Wilson v, Jul 12 2014 *)
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PROG
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(PARI) x='x+O('x^50); Vec((1+x^2)/(1-x-x^3)) \\ G. C. Greubel, Apr 26 2017
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CROSSREFS
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Cf. A068927 for incongruent tilings, A068920 for more info.
Cf. A000930, A078012, first column of A272471.
Sequence in context: A247083 A159848 A017826 * A000930 A078012 A135851
Adjacent sequences: A068918 A068919 A068920 * A068922 A068923 A068924
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KEYWORD
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nonn,easy
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AUTHOR
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Dean Hickerson, Mar 11 2002
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STATUS
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approved
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