Hypocycloid and Lattice points (noch nicht übersetzt)

Problem 450

A hypocycloid is the curve drawn by a point on a small circle rolling inside a larger circle. The parametric equations of a hypocycloid centered at the origin, and starting at the right most point is given by:

x(t)=(Rr)cos(t)+rcos(Rrrt) y(t)=(Rr)sin(t)rsin(Rrrt)

Where R is the radius of the large circle and r the radius of the small circle.

Let C(R,r) be the set of distinct points with integer coordinates on the hypocycloid with radius R and r and for which there is a corresponding value of t such that sin(t) and cos(t) are rational numbers.

Let S(R,r)=(x,y)C(R,r)|x|+|y| be the sum of the absolute values of the x and y coordinates of the points in C(R,r).

Let T(N)=NR=3R12r=1S(R,r) be the sum of S(R,r) for R and r positive integers, RN and 2r<R.

You are given:

C(3,1) = {(3,0),(1,2),(1,0),(1,2)}
C(2500,1000) = {(2500,0),(772,2376),(772,2376),(516,1792),(516,1792),(500,0),(68,504),(68,504),
  (1356,1088),(1356,1088),(1500,1000),(1500,1000)}

Note: (625,0) is not an element of C(2500,1000) because sin(t) is not a rational number for the corresponding values of t.

S(3,1)=(|3|+|0|)+(|1|+|2|)+(|1|+|0|)+(|1|+|2|)=10

T(3)=10;T(10)=524;T(100)=580442;T(103)=583108600.

Find T(106).