Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.
A123773
Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.
Terms
- a(0) =1a(1) =1a(2) =3a(3) =4a(4) =16a(5) =24a(6) =103a(7) =163a(8) =721a(9) =1173a(10) =5283a(11) =8783a(12) =39912a(13) =67381a(14) =308314a(15) =526553a(16) =2421040a(17) =4172834a(18) =19257309a(19) =33438244a(20) =154761065a(21) =270372085
External references
- oeis: A123773