Quatro-safe primes.

Terms

a(0) =47a(1) =1439a(2) =2879a(3) =858239a(4) =861599a(5) =982559a(6) =1014719a(7) =1067999a(8) =2029439a(9) =2034239a(10) =2297759a(11) =2683679a(12) =2978399a(13) =3301919a(14) =4068479a(15) =4288799a(16) =4737599a(17) =5454719a(18) =6484319a(19) =6753119a(20) =7145759a(21) =8624159a(22) =9511199a(23) =9717119a(24) =10533599a(25) =10739999