52154domain: NAppears in sequencesNumbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 18.at n=20A031606Values of x in A216363.at n=25A216382G.f. satisfies: A(x) = x + A( A(x)^2 - A(x)^5 ).at n=10A275755