Number of ways to build a contiguous building with n LEGO blocks of size 3 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

A123836

Number of ways to build a contiguous building with n LEGO blocks of size 3 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

Terms

    a(0) =1a(1) =9a(2) =17a(3) =186a(4) =523a(5) =6478a(6) =19077a(7) =247945a(8) =796692

External references