47167domain: NAppears in sequencesNumbers k such that the period of the continued fraction for sqrt(k) contains exactly 69 ones.at n=1A031837Numbers n such that 69*2^n-1 is prime.at n=50A050560E.g.f.: Sum_{n>=0} x^n/n! * LambertW(-n*x)/(-n*x).at n=6A230323