Number of ways to build a contiguous building with n LEGO blocks of size 1 X 4 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

A123783

Number of ways to build a contiguous building with n LEGO blocks of size 1 X 4 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) =11a(2) =21a(3) =248a(4) =712a(5) =9182a(6) =28297a(7) =375483a(8) =1266013

External references