title: Find the longest sequence using a starting number under one million. url: http://projecteuler.net/problem=15 desc: | Starting in the top left corner of a 22 grid, there are 6 routes (without backtracking) to the bottom right corner. How many routes are there through a 2020 grid? solution: | (2n)!/n!^2 - Where n is the size of the grid - todo: Find a more "programmable way" instead of this cheating mathsolution solutions: solve.php: desc: Using BCMath to cope with large numbers language: php solve.rb: desc: Basic solution language: ruby