A123803 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x7 which is symmetric after a rotation by 180 degrees.

1, 2, 52, 617, 6052, 86534, 814679, 12560687

Offset

1,2

Links

Table of n, a(n) for n=1..8.

Crossrefs

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

Sequence in context: A300104 A034311 A053317 * A284767 A101930 A297756

Adjacent sequences: A123800 A123801 A123802 * A123804 A123805 A123806

Keyword

nonn,more

Author

Søren Eilers, Oct 29 2006

Status

approved