53385domain: NAppears in sequencesa(n) = Sum_{k=0..floor(n/2)} T(n-k,k), T given by A026780.at n=19A026790Number of ways to place zero or more nonadjacent 1,0 2,0 3,1 3,2 3,3 4,1 5,2 polyhexes in any orientation on a planar nXnXn triangular grid.at n=8A155340Size of the edge set of the Generalized Lucas Cube Q_n(111).at n=15A219355