A123820 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 90 degrees.

1, 1, 1, 1, 3, 4, 5, 10, 26, 38, 51, 121, 324, 488, 673, 1808

Offset

1,5

Links

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

Crossrefs

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

Sequence in context: A342333 A369789 A136366 * A261903 A133320 A225906

Adjacent sequences: A123817 A123818 A123819 * A123821 A123822 A123823

Keyword

nonn

Author

Søren Eilers, Oct 29 2006

Status

approved