Number of compositions of n with all adjacent parts (x, y) satisfying x >= 2y or y >= 2x.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =5a(6) =10a(7) =18a(8) =26a(9) =42a(10) =72a(11) =114a(12) =184a(13) =305a(14) =494a(15) =799a(16) =1305a(17) =2123a(18) =3446a(19) =5611a(20) =9134a(21) =14851a(22) =24162a(23) =39314a(24) =63945a(25) =104025a(26) =169238a(27) =275305a(28) =447863a(29) =728592