51107domain: NAppears in sequencesa(n) = C(n,5) + C(n,4) - C(n,3) + 1, n >= 7.at n=18A005288Number of ways to place zero or more nonadjacent 0,0 1,0 2,0 3,1 4,2 5,3 6,3 7,3 polyhexes in any orientation on a planar nXnXn triangular grid.at n=8A155403Number of reduced words of length n in the Weyl group A_21.at n=5A161518