A123779 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x4 which is symmetric after a rotation by 180 degrees.

1, 1, 21, 67, 849, 3185, 39868, 162562, 2027829

Offset

1,3

Links

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

Crossrefs

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

Sequence in context: A219814 A219379 A168240 * A123839 A180758 A197121

Adjacent sequences: A123776 A123777 A123778 * A123780 A123781 A123782

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Status

approved