Problem 131 - prime cube partnership

 - Recognised the first few solutions as Cuban primes
 - Simply count the number of cubans < 1000000
Problem 131 - Prime cuban partnership, proof added.

 - Added derivation in comments for the solution.
 - First establish that n is a cube, and p+n is a cube.
 - Implies p is a difference of cubes
 - But given p is prime, and the difference of cubes formula:
   y^3 - x^3 = (y-x)(y^2 + xy + x^2),
   then y-x must be 1.
 - Hence p is the difference of consecutive cubes.
 - Therefore, code searches for prime consecutive cube differences.
 - Code only trivially changed to match the math in comments