698709domain: NAppears in sequencesNumber of Barlow packings with group P3(bar)m1(S) that repeat after 2n layers.at n=22A011951Number of Barlow packings with group P3(bar)m1(O) that repeat after 2n layers.at n=18A011952a(n) = 3*a(n-1) - 4*a(n-2) + 6*a(n-3) - 4*a(n-4), with initial terms 0,0,0,1.at n=22A136401