Tribonacci-like sequence; a(0)=2, a(1)=1, a(2)=1, a(n) = a(n-1) + a(n-2) + a(n-3).

Terms

a(0) =2a(1) =1a(2) =1a(3) =4a(4) =6a(5) =11a(6) =21a(7) =38a(8) =70a(9) =129a(10) =237a(11) =436a(12) =802a(13) =1475a(14) =2713a(15) =4990a(16) =9178a(17) =16881a(18) =31049a(19) =57108a(20) =105038a(21) =193195a(22) =355341a(23) =653574a(24) =1202110a(25) =2211025a(26) =4066709a(27) =7479844a(28) =13757578a(29) =25304131