a(1) = 2; thereafter, if a(n-1) is prime then a(n) = prime(n) + 1; otherwise a(n) = 2*a(n-1) - 1.

Terms

a(0) =2a(1) =4a(2) =7a(3) =8a(4) =15a(5) =29a(6) =18a(7) =35a(8) =69a(9) =137a(10) =32a(11) =63a(12) =125a(13) =249a(14) =497a(15) =993a(16) =1985a(17) =3969a(18) =7937a(19) =72a(20) =143a(21) =285a(22) =569a(23) =90a(24) =179a(25) =102a(26) =203a(27) =405a(28) =809a(29) =114