Fourth root of largest n-digit number with exactly five divisors.

Terms

a(0) =3a(1) =5a(2) =7a(3) =17a(4) =31a(5) =53a(6) =97a(7) =173a(8) =313a(9) =557a(10) =997a(11) =1777a(12) =3137a(13) =5623a(14) =9973a(15) =17761a(16) =31607a(17) =56209a(18) =99991a(19) =177823a(20) =316223a(21) =562337a(22) =999983a(23) =1778279a(24) =3162277a(25) =5623403a(26) =9999991a(27) =17782769a(28) =31622743a(29) =56234069