A123787 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x5 which is symmetric after a rotation by 180 degrees.

1, 2, 28, 192, 1680, 13644, 118916, 1044873, 9160772

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Crossrefs

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

Sequence in context: A280120 A065340 A001798 * A035601 A281124 A244721

Adjacent sequences: A123784 A123785 A123786 * A123788 A123789 A123790

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Status

approved