1,1

Also numbers n such that (7*10^n-61)/9 is prime.

Index entries for primes involving repunits

Makoto Kamada, Factorizations of 77...771.

a(n)=A056688(n)+1 - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

Do[ If[ PrimeQ[ 7(10^n - 1)/9 - 6], Print[n]], {n, 0, 7000}]

Sequence in context: A121181 A007355 A105452 this_sequence A061871 A084651 A085509

Adjacent sequences: A099416 A099417 A099418 this_sequence A099420 A099421 A099422

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2004

7163 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008