1,2

Also numbers n such that (4*10^n-13)/9 is prime.

Index entries for primes involving repunits

n=30 means that 444444444444444444444444444443 is prime.

Do[ If[ PrimeQ[ 4(10^n - 1)/9 - 1], Print[n]], {n, 5000}] (from Robert G. Wilson v Oct 14 2004)

Cf. A096503-A096508, A096841-A096846, A000203.

Sequence in context: A144677 A058616 A123316 this_sequence A130673 A062891 A018599

Adjacent sequences: A096842 A096843 A096844 this_sequence A096846 A096847 A096848

hard,more,nonn

Labos E. (labos(AT)ana.sote.hu), Jul 15 2004