Numbers k such that 5*R_k + 7*10^k + 2 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

A259132

Numbers k such that 5*R_k + 7*10^k + 2 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

Terms

    a(0) =2a(1) =4a(2) =10a(3) =20a(4) =22a(5) =58a(6) =74a(7) =82a(8) =208a(9) =350a(10) =422a(11) =3812a(12) =3982a(13) =20924a(14) =23786a(15) =38852a(16) =56042a(17) =68504a(18) =74434

External references