Number of ways to build a contiguous building with n LEGO blocks of size 1 X 5 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

A123791

Number of ways to build a contiguous building with n LEGO blocks of size 1 X 5 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) =2a(1) =16a(2) =56a(3) =552a(4) =2722a(5) =30836a(6) =164018a(7) =1941658

External references