4783023domain: NAppears in sequencesNumbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 81.at n=26A031759a(n) = Sum_{d|7} phi(d)*n^(7/d).at n=9A054606a(n) = Sum_{d|n} phi(d)*9^(n/d).at n=7A054616Triangle T(n,k) = Sum_{d|k} phi(d)*n^(k/d).at n=42A054619