Numbers n such that 3*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A102980

Numbers n such that 3*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =2a(1) =3a(2) =6a(3) =17a(4) =20a(5) =45a(6) =57a(7) =78a(8) =119a(9) =137a(10) =509a(11) =710a(12) =1127a(13) =1518a(14) =1761a(15) =3086a(16) =3147a(17) =9926a(18) =19854a(19) =27842a(20) =46799a(21) =49682a(22) =68718a(23) =100542a(24) =106649a(25) =191073

External references