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A123818
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Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2.
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0
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1, 3, 31, 412, 6435, 106108, 1825803, 32320892, 584956651, 10772558067, 201219520632
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..11.
S. Eilers, The LEGO counting problem, Amer. Math. Mnthly, 123 (May 2016), 415-426.
Index entry for sequences related to LEGO blocks
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CROSSREFS
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Cf. A112389, A123762-A123827, A123829-A123849.
Sequence in context: A136596 A186207 A014178 * A087591 A061053 A047798
Adjacent sequences: A123815 A123816 A123817 * A123819 A123820 A123821
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KEYWORD
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nonn,hard,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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