999800domain: NAppears in sequencesa(n) = a(n-1) + a(n-2) + 1, with a(0) = 1 and a(1) = 6.at n=26A022320Numbers X such that X^2 + Y^2 = 10^(2*k) + 1, with X > Y > 0 and k is the decimal digit length of X-1.at n=13A368418