1,2

Also numbers n such that (11*10^n+7)/9 is prime.

Makoto Kamada, Factorizations of 122...223.

Index entries for primes involving repunits.

Do[ If[ PrimeQ[(11*10^n + 7)/9], Print[n]], {n, 0, 10000}]

Sequence in context: A018445 A129432 A111551 this_sequence A105458 A001530 A012063

Adjacent sequences: A102926 A102927 A102928 this_sequence A102930 A102931 A102932

more,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004