A123818 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2.

1, 3, 31, 412, 6435, 106108, 1825803, 32320892, 584956651, 10772558067, 201219520632

Offset: 1

Author

Søren Eilers, Oct 29 2006

Keywords

• nonn
• hard
• more

Links

• S. Eilers, The LEGO counting problem, Amer. Math. Mnthly, 123 (May 2016), 415-426.
• Index entry for sequences related to LEGO blocks

Crossrefs

Cf. A112389, A123762-A123827, A123829-A123849.