Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) with a(0)=3, a(1)=4, a(2)=5.

Terms

a(0) =3a(1) =4a(2) =5a(3) =12a(4) =21a(5) =38a(6) =71a(7) =130a(8) =239a(9) =440a(10) =809a(11) =1488a(12) =2737a(13) =5034a(14) =9259a(15) =17030a(16) =31323a(17) =57612a(18) =105965a(19) =194900a(20) =358477a(21) =659342a(22) =1212719a(23) =2230538a(24) =4102599a(25) =7545856a(26) =13878993a(27) =25527448a(28) =46952297a(29) =86358738