Number of compositions of n avoiding the pattern (2,1,2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =15a(6) =29a(7) =55a(8) =103a(9) =190a(10) =347a(11) =630a(12) =1134a(13) =2028a(14) =3585a(15) =6291a(16) =10950a(17) =18944a(18) =32574a(19) =55692a(20) =94618a(21) =159758a(22) =268147a(23) =447502a(24) =743097a(25) =1227910a(26) =2020110a(27) =3308302a(28) =5394617a(29) =8757108