A123781 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 4 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

1, 1, 5, 7, 41, 65, 384, 649, 3853, 6745, 40209, 72334, 431188, 791144, 4717533, 8787824, 52396271, 98784645

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