Circular arcs

For each natural number k, let C(k) denote the circle with radius k units and centre at origin O, on the circle C(k) a particle moves k centimeters in the counter-clockwise direction. After completing its motion on C(k), particle moves to C(k+1) in the radial direction.The motion of particle continues in this manner.The particle starts at (1,0).If the particle crosses +ve x-axis first time on C(n), then n = ?... Enter Your answer as sum of digits of $\frac{45n}{7}$ ..