A123819 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2 which is symmetric after a rotation by 180 degrees.

1, 1, 5, 8, 65, 126, 1023, 2187, 17585, 39606, 315326, 737302

Offset

1,3

Links

Table of n, a(n) for n=1..12.

Crossrefs

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

Sequence in context: A132050 A250067 A213239 * A286076 A302651 A260695

Adjacent sequences: A123816 A123817 A123818 * A123820 A123821 A123822

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Status

approved