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

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =13a(6) =23a(7) =40a(8) =67a(9) =115a(10) =190a(11) =311a(12) =505a(13) =807a(14) =1285a(15) =2031a(16) =3164a(17) =4896a(18) =7550a(19) =11499a(20) =17480a(21) =26379a(22) =39558a(23) =58946a(24) =87469a(25) =129051a(26) =189484a(27) =277143a(28) =403477a(29) =584653