A123825 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2x3 which is symmetric after a rotation by 180 degrees.

1, 1, 25, 53, 1189, 2947, 66094, 181955, 3979943

Offset

1,3

Links

Table of n, a(n) for n=1..9.

Crossrefs

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

Sequence in context: A118304 A117472 A146633 * A349416 A157269 A186892

Adjacent sequences: A123822 A123823 A123824 * A123826 A123827 A123828

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Status

approved