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A123848
Number of ways to build a contiguous building with n LEGO blocks of size 5 X 5 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.
0
1, 29, 57, 1955, 5805, 222291, 694961
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: A339865 A033915 A192358 * A340669 A040812 A184081
KEYWORD
nonn,more
AUTHOR
Søren Eilers, Oct 29 2006
STATUS
approved