a(n) = ceiling(x(n)), where x(n) = 3*x(n-1)/2 and x(1) = 1.

Terms

a(0) =2a(1) =3a(2) =5a(3) =7a(4) =11a(5) =16a(6) =23a(7) =35a(8) =52a(9) =77a(10) =116a(11) =173a(12) =260a(13) =390a(14) =584a(15) =876a(16) =1314a(17) =1971a(18) =2956a(19) =4434a(20) =6651a(21) =9976a(22) =14964a(23) =22446a(24) =33669a(25) =50503a(26) =75754a(27) =113631a(28) =170446a(29) =255669