Greatest prime divisor of prime(n) - 3.

Terms

a(0) =2a(1) =2a(2) =2a(3) =5a(4) =7a(5) =2a(6) =5a(7) =13a(8) =7a(9) =17a(10) =19a(11) =5a(12) =11a(13) =5a(14) =7a(15) =29a(16) =2a(17) =17a(18) =7a(19) =19a(20) =5a(21) =43a(22) =47a(23) =7a(24) =5a(25) =13a(26) =53a(27) =11a(28) =31a(29) =2