Project Euler > Problem 15 > Lattice paths (Java Solution)

Problem:

Starting in the top left corner of a 2[×]2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.

How many such routes are there through a 20[×]20 grid?

Solution:

137846528820

Code:
The solution may include methods that will be found here: Library.java .

public interface EulerSolution{

public String run();

}

/* 
 * Solution to Project Euler problem 15
 * By Nayuki Minase
 * 
 * http://nayuki.eigenstate.org/page/project-euler-solutions
 * https://github.com/nayuki/Project-Euler-solutions
 */


public final class p015 implements EulerSolution {
 
 public static void main(String[] args) {
  System.out.println(new p015().run());
 }
 
 
 public String run() {
  return Library.binomial(40, 20).toString();
 }
 
}