a(n) is the number of compositions of n in which the maximal part is 3.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =5a(6) =11a(7) =23a(8) =47a(9) =94a(10) =185a(11) =360a(12) =694a(13) =1328a(14) =2526a(15) =4781a(16) =9012a(17) =16929a(18) =31709a(19) =59247a(20) =110469a(21) =205606a(22) =382087a(23) =709108a(24) =1314512a(25) =2434364a(26) =4504352a(27) =8328253a(28) =15388362a(29) =28417385