Greatest prime divisor of prime(n) - 1.

Terms

a(0) =2a(1) =2a(2) =3a(3) =5a(4) =3a(5) =2a(6) =3a(7) =11a(8) =7a(9) =5a(10) =3a(11) =5a(12) =7a(13) =23a(14) =13a(15) =29a(16) =5a(17) =11a(18) =7a(19) =3a(20) =13a(21) =41a(22) =11a(23) =3a(24) =5a(25) =17a(26) =53a(27) =3a(28) =7a(29) =7