a(1) = 9; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.

Terms

a(0) =9a(1) =11a(2) =21a(3) =33a(4) =39a(5) =71a(6) =73a(7) =81a(8) =101a(9) =123a(10) =193a(11) =257a(12) =271a(13) =293a(14) =379a(15) =387a(16) =407a(17) =627a(18) =669a(19) =931a(20) =1073a(21) =1179a(22) =1273a(23) =1481a(24) =2587a(25) =2627a(26) =2923a(27) =3063a(28) =3617a(29) =3931