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A123763
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Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 2 which is symmetric after a rotation by 180 degrees.
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0
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1, 1, 7, 11, 76, 135, 942, 1812, 12537, 25246, 174019, 362458, 2485725
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OFFSET
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1,3
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LINKS
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Table of n, a(n) for n=1..13.
M. Abrahamsen and S. Eilers, On the asymptotic enumeration of LEGO structures, Exper Math. 20 (2) (2011) 145-152.
B. Durhuus and S. Eilers, On the entropy of LEGO, arXiv:math/0504039 [math.CO], 2005.
S. Eilers, A LEGO Counting problem, 2005.
S. Eilers, The LEGO counting problem, Amer. Math. Monthly, 123 (May 2016), 415-426.
Index entry for sequences related to LEGO blocks
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CROSSREFS
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Sequence in context: A061809 A289286 A337099 * A018680 A107187 A132958
Adjacent sequences: A123760 A123761 A123762 * A123764 A123765 A123766
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KEYWORD
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nonn,more
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AUTHOR
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Søren Eilers, Oct 29 2006
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STATUS
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approved
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