%N Number of ways to build a contiguous building with n LEGO blocks of size 2 X 2 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.
%C The base block is not counted among the n and must be the only block in the bottom layer of the building
%Y Cf. A112389, A123762 - A123827, A123829 - A123849.
%A _Søren Eilers_, Oct 29 2006