A123813 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 8 which is flat, i.e., with all blocks in parallel position, and symmetric after a rotation by 180 degrees.

1, 1, 9, 13, 153, 249, 3011, 5209, 63991, 114321, 1421173, 2603433, 32518012, 60650817, 760402013, 1437977218

Offset

1,3

Links

Table of n, a(n) for n=1..16.

Crossrefs

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

Sequence in context: A166662 A108748 A116106 * A147498 A115445 A131602

Adjacent sequences: A123810 A123811 A123812 * A123814 A123815 A123816

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Extensions

a(11)-a(16) from Søren Eilers, Sep 14 2018

Status

approved