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.

1, 1, 7, 11, 76, 135, 942, 1812, 12537, 25246, 174019, 362458, 2485725

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 A347170 A107187

Adjacent sequences: A123760 A123761 A123762 * A123764 A123765 A123766

Keyword

nonn,more

Author

Søren Eilers, Oct 29 2006

Status

approved