4707712domain: NAppears in sequencesNumber of 2n-bead black-white reversible complementable necklaces with n black beads and fundamental period 2n.at n=16A045633Number of nX3 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 3,2,1,1,1 for x=0,1,2,3,4.at n=9A197777