Number of ferrites M_2Y_n that repeat after 6n+10 layers.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =1a(7) =2a(8) =2a(9) =2a(10) =2a(11) =3a(12) =2a(13) =3a(14) =3a(15) =3a(16) =3a(17) =4a(18) =3a(19) =4