Numbers n such that 3*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A102968

Numbers n such that 3*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =3a(1) =5a(2) =9a(3) =12a(4) =27a(5) =51a(6) =53a(7) =147a(8) =155a(9) =257a(10) =519a(11) =603a(12) =2885a(13) =9509a(14) =10524a(15) =19650a(16) =32508a(17) =79445a(18) =158909

External references