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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =8a(7) =12a(8) =17a(9) =24a(10) =34a(11) =51a(12) =73a(13) =106a(14) =155a(15) =224a(16) =328a(17) =477a(18) =695a(19) =1013a(20) =1477a(21) =2154a(22) =3140a(23) =4578a(24) =6673a(25) =9728a(26) =14176a(27) =20663a(28) =30113a(29) =43882