Number of ferrites M_6Y_n that repeat after 6n+30 layers.

Terms

a(0) =0a(1) =2a(2) =3a(3) =6a(4) =9a(5) =19a(6) =24a(7) =46a(8) =62a(9) =96a(10) =132a(11) =194a(12) =249a(13) =354a(14) =452a(15) =600a(16) =762a(17) =986a(18) =1212a(19) =1544