Numbers such that every prefix and suffix is 1 or a prime.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =11a(6) =13a(7) =17a(8) =23a(9) =31a(10) =37a(11) =53a(12) =71a(13) =73a(14) =113a(15) =131a(16) =137a(17) =173a(18) =197a(19) =311a(20) =313a(21) =317a(22) =373a(23) =797a(24) =1373a(25) =1997a(26) =3137a(27) =3797a(28) =7331a(29) =73331