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) =3a(5) =3a(6) =7a(7) =9a(8) =9a(9) =16a(10) =21a(11) =22a(12) =36a(13) =47a(14) =51a(15) =77a(16) =101a(17) =114a(18) =165a(19) =217a(20) =251a(21) =350a(22) =459a(23) =540a(24) =733a(25) =962a(26) =1152a(27) =1535a(28) =2010a(29) =2437