64335domain: NAppears in sequencesNumber of ways to build a contiguous building with n LEGO blocks of size 1 X 2 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position.at n=7A123768Expansion of Sum_{k>0} (1/(1-x^k)^5 - 1).at n=31A363695