A123797 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 6 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

1, 1, 7, 10, 88, 142, 1277, 2193, 19967, 35449, 325809, 593589, 5473435, 10159187, 93929982, 176846933

Offset: 1

Author

Søren Eilers, Oct 29 2006

Keywords

• nonn
• more

Crossrefs

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

Extensions

More terms by Søren Eilers, Sep 12 2018