← Complete problem index

PROJECT EULER · #0404

Crisscross Ellipses

Statement only · UnsolvedOriginal problem ↗

Ea is an ellipse with an equation of the form x2+4y2=4a2.
Ea is the rotated image of Ea by θ degrees counterclockwise around the origin O(0,0) for 0<θ<90.

0404_c_ellipse.gif

b is the distance to the origin of the two intersection points closest to the origin and c is the distance of the two other intersection points.
We call an ordered triplet (a,b,c) a canonical ellipsoidal triplet if a,b and c are positive integers.
For example, (209,247,286) is a canonical ellipsoidal triplet.

Let C(N) be the number of distinct canonical ellipsoidal triplets (a,b,c) for aN.
It can be verified that C(103)=7, C(104)=106 and C(106)=11845.

Find C(1017).

Write-up coming later

The complete problem is available here. An approach, code, and answer will be added later.