Numbers k such that (86*10^k - 221)/9 is prime.

Terms

a(0) =1a(1) =4a(2) =7a(3) =13a(4) =17a(5) =31a(6) =47a(7) =64a(8) =226a(9) =251a(10) =268a(11) =310a(12) =352a(13) =394a(14) =478a(15) =599a(16) =1529a(17) =1679a(18) =11590a(19) =12922a(20) =13151a(21) =18808a(22) =47188a(23) =52450a(24) =83038a(25) =93217a(26) =128086a(27) =154853a(28) =175774