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A123801 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 6 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees. 0
1, 4, 7, 31, 76, 365, 920, 4691, 12695, 65708, 184458, 967195, 2798734, 14837523, 43829052, 234029147, 703643181 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The base block is not counted among the n and must be the only block in the bottom layer of the building.
LINKS
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.CO/0504039
CROSSREFS
Sequence in context: A080871 A358586 A102666 * A359706 A156228 A218959
KEYWORD
nonn
AUTHOR
Søren Eilers, Oct 29 2006
EXTENSIONS
a(12)-a(17) from Søren Eilers, Sep 16 2018
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)