Largest prime <= square root of 10^n.

Terms

a(0) =3a(1) =7a(2) =31a(3) =97a(4) =313a(5) =997a(6) =3137a(7) =9973a(8) =31607a(9) =99991a(10) =316223a(11) =999983a(12) =3162277a(13) =9999991a(14) =31622743a(15) =99999989a(16) =316227731a(17) =999999937a(18) =3162277633a(19) =9999999967a(20) =31622776589a(21) =99999999977a(22) =316227766003a(23) =999999999989