A123765 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 2 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.
1, 1, 3, 4, 12, 18, 52, 83, 235, 389, 1087, 1851, 5113, 8891, 24357, 43045, 117127, 209731, 567487, 1027245, 2766404, 5053521, 13554315, 24954627, 66696366, 123628610, 329400200, 614216837, 1632039074, 3059240151, 8108703876
Offset: 1
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
- S. Eilers, The LEGO counting problem, Amer. Math. Monthly, 123 (May 2016), 415-426.
- Index entry for sequences related to LEGO blocks
Extensions
More terms by Søren Eilers, Sep 12 2018