a(n) = floor(a(n-1)*3/2) with a(1) = 2.

Terms

a(0) =2a(1) =3a(2) =4a(3) =6a(4) =9a(5) =13a(6) =19a(7) =28a(8) =42a(9) =63a(10) =94a(11) =141a(12) =211a(13) =316a(14) =474a(15) =711a(16) =1066a(17) =1599a(18) =2398a(19) =3597a(20) =5395a(21) =8092a(22) =12138a(23) =18207a(24) =27310a(25) =40965a(26) =61447a(27) =92170a(28) =138255a(29) =207382