30986domain: NAppears in sequencesNumbers k such that the continued fraction for sqrt(k) has period 47.at n=36A020386a(n) = C(2,n) DELTA C(0,n).at n=49A147721a(1) = 1; a(n) = a(n-1) + Sum_{k=2..n} a(floor(n/k)).at n=48A351620a(n) is the least number k such that A380802(k) = n, or -1 if no such number exists.at n=21A380803