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Search: id:A068921
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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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+0
7
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| 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
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) = A000930(n+4).
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FORMULA
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For n >= 4, a(n) = a(n-1) + a(n-3).
Contribution from Frank Ruskey (ruskey(AT)cs.uvic.ca), Jun 07 2009: (Start)
Generating function (with a(0)=1): (1+z^2)/(1-z-z^3).
Formula: SUM( binomial(n-2j+1,j), j >= 0 ). (End)
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CROSSREFS
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Cf. A068927 for incongruent tilings, A068920 for more info.
Cf. A078012.
Sequence in context: A159848 A017826 A000930 this_sequence A078012 A135851 A101913
Adjacent sequences: A068918 A068919 A068920 this_sequence A068922 A068923 A068924
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KEYWORD
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easy,nonn
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AUTHOR
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Dean Hickerson (dean.hickerson(AT)yahoo.com), Mar 11 2002
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