a(n) is the largest prime < 3*a(n-1) for n > 1, with a(1) = 2.

Terms

a(0) =2a(1) =5a(2) =13a(3) =37a(4) =109a(5) =317a(6) =947a(7) =2837a(8) =8501a(9) =25471a(10) =76403a(11) =229199a(12) =687593a(13) =2062759a(14) =6188263a(15) =18564769a(16) =55694299a(17) =167082893a(18) =501248653a(19) =1503745949a(20) =4511237741a(21) =13533713213a(22) =40601139629a(23) =121803418861a(24) =365410256543