A123835 Number of ways to build a contiguous building with n LEGO blocks of size 3 X 3 on top of a fixed block of the same size.

25, 757, 29925, 1281402, 59340183, 2862828262, 142920335981, 7311973715989

Offset

1,1

Comments

The base block is not counted among the n and must be the only block in the bottom layer of the building

Links

Table of n, a(n) for n=1..8.

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: A217996 A246906 A286439 * A012835 A277584 A223228

Adjacent sequences: A123832 A123833 A123834 * A123836 A123837 A123838

Keyword

nonn,hard

Author

Søren Eilers, Oct 29 2006

Status

approved