login
A123833
Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 3 X 3 which is symmetric after a rotation by 180 degrees.
0
1, 1, 9, 22, 317, 980, 13801, 48756, 660997, 2505447
OFFSET
1,3
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: A264651 A113519 A300462 * A156342 A133769 A358156
KEYWORD
nonn
AUTHOR
Søren Eilers, Oct 29 2006
STATUS
approved