Number of compositions of n avoiding the patterns (1,2,3) and (3,2,1).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =16a(6) =30a(7) =56a(8) =100a(9) =173a(10) =293a(11) =482a(12) =779a(13) =1232a(14) =1928a(15) =2972a(16) =4546a(17) =6894a(18) =10435a(19) =15705a(20) =23692a(21) =35679a(22) =53976a(23) =81760a(24) =124611a(25) =190404a(26) =292871a(27) =452070a(28) =702042a(29) =1094034