A123789 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 5 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

1, 1, 5, 7, 49, 77, 572, 949, 7245, 12361, 96063, 167564, 1313467, 2327488, 18365795, 32936281, 261111133, 472694546

Offset

1,3

Links

Table of n, a(n) for n=1..18.

Crossrefs

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

Sequence in context: A299452 A110420 A210244 * A367572 A180552 A168545

Adjacent sequences: A123786 A123787 A123788 * A123790 A123791 A123792

Keyword

nonn,more

Author

Søren Eilers, Oct 29 2006

Extensions

More terms by Søren Eilers, Sep 12 2018

Status

approved