89645domain: NAppears in sequencesa(n) = Sum_{k=0..floor(n/2)} T(n,k) * T(n,k+1), with T given by A026009.at n=9A027288Numbers 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 20.at n=25A031608