1,2

Also numbers n such that 2*10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Makoto Kamada, Factorizations of 299...993.

Index entries for primes involving repunits.

Do[ If[ PrimeQ[3*10^n-7], Print[n]], {n, 0, 10000}]

Sequence in context: A120896 A074801 A006401 this_sequence A075885 A018377 A056363

Adjacent sequences: A102961 A102962 A102963 this_sequence A102965 A102966 A102967

more,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 17 2004