Number of compositions of n that avoid the pattern 12-3.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =16a(6) =31a(7) =60a(8) =114a(9) =215a(10) =402a(11) =746a(12) =1375a(13) =2520a(14) =4593a(15) =8329a(16) =15036a(17) =27027a(18) =48389a(19) =86314a(20) =153432a(21) =271853a(22) =480207a(23) =845804a(24) =1485703a(25) =2603018a(26) =4549521a(27) =7933239a(28) =13803293a(29) =23966682