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A123763 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 2 which is symmetric after a rotation by 180 degrees. 0
1, 1, 7, 11, 76, 135, 942, 1812, 12537, 25246, 174019, 362458, 2485725 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..13.

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/0504039 [math.CO], 2005.

S. Eilers, A LEGO Counting problem, 2005.

S. Eilers, The LEGO counting problem, Amer. Math. Monthly, 123 (May 2016), 415-426.

Index entry for sequences related to LEGO blocks

CROSSREFS

Sequence in context: A061809 A289286 A337099 * A018680 A107187 A132958

Adjacent sequences:  A123760 A123761 A123762 * A123764 A123765 A123766

KEYWORD

nonn,more

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified January 27 14:29 EST 2021. Contains 340467 sequences. (Running on oeis4.)