Numbers k such that 60*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

a(0) =1a(1) =2a(2) =3a(3) =9a(4) =17a(5) =20a(6) =21a(7) =27a(8) =42a(9) =65a(10) =120a(11) =132a(12) =177a(13) =240a(14) =453a(15) =552a(16) =1599a(17) =2174a(18) =2977a(19) =3648a(20) =7707a(21) =8315a(22) =10391a(23) =12457a(24) =21056a(25) =26222a(26) =48296a(27) =64040a(28) =84903a(29) =92975