Number of Barlow packings that repeat after n (or a divisor of n) layers.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =1a(5) =4a(6) =3a(7) =8a(8) =8a(9) =18a(10) =21a(11) =48a(12) =63a(13) =133a(14) =205a(15) =412a(16) =685a(17) =1354a(18) =2385a(19) =4644a(20) =8496a(21) =16431a(22) =30735a(23) =59344a(24) =112531a(25) =217246a(26) =415628a(27) =803210a(28) =1545463a(29) =2991192