Numbers n such that 6*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103035
Numbers n such that 6*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =0a(1) =2a(2) =5a(3) =6a(4) =11a(5) =15a(6) =69a(7) =90a(8) =134a(9) =189a(10) =245a(11) =267a(12) =270a(13) =470a(14) =1575a(15) =2295a(16) =2507a(17) =3512a(18) =3825a(19) =6857a(20) =11022a(21) =11657a(22) =17499a(23) =35036a(24) =41966a(25) =50558a(26) =93062
External references
- oeis: A103035