Number of gap-free compositions of n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =11a(5) =21a(6) =39a(7) =71a(8) =141a(9) =276a(10) =542a(11) =1070a(12) =2110a(13) =4189a(14) =8351a(15) =16618a(16) =33134a(17) =66129a(18) =131937a(19) =263483a(20) =526453a(21) =1051984a(22) =2102582a(23) =4203177a(24) =8403116a(25) =16800894a(26) =33593742a(27) =67174863a(28) =134328816a(29) =268624026