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A123768
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Number of ways to build a contiguous building with n LEGO blocks of size 1x2 on top of a fixed block of the same size so that the builing is flat, i.e. with all blocks in parallel position.
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0
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3, 10, 39, 160, 693, 3071, 13953, 64335, 300749, 1420116, 6764691, 32453268, 156653477, 760139341, 3705381789, 18134664515, 89068494994, 438841011495
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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
| 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
| S. Eilers, LEGO counts
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CROSSREFS
| Sequence in context: A151067 A007163 A050385 * A005750 A151068 A151069
Adjacent sequences: A123765 A123766 A123767 * A123769 A123770 A123771
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KEYWORD
| nonn,hard
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AUTHOR
| Soren Eilers (eilers(AT)math.ku.dk), Oct 29 2006
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