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Search: id:A123785
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| A123785 |
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Number of ways to build a contiguous building with n LEGO blocks of size 1x4 on top of a fixed block of the same size so that the builing is flat, i.e. with all blocks in parallel position, and symmetric after a rotation by 180 degrees. |
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+0
1
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| 1, 3, 5, 16, 36, 124, 287, 1043, 2573, 9448, 24161, 89827, 235902
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The base block is not counted among the n, and must be the only block in the bottom layer of the building
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REFERENCES
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M. Abrahamsen and S. Eilers, Efficient counting of LEGO buildings, in preparation
B. Durhuus and S. Eilers, On the entropy of LEGO, arXiv:math.CO/0504039
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LINKS
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S. Eilers, LEGO counts
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CROSSREFS
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Adjacent sequences: A123782 A123783 A123784 this_sequence A123786 A123787 A123788
Sequence in context: A019096 A077551 A106588 this_sequence A121646 A099101 A038120
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KEYWORD
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nonn
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AUTHOR
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Soren Eilers (eilers(AT)math.ku.dk), Oct 29 2006
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