Home to the 'definitive' list of Four Fours solutions. There's a solution for all whole numbers up to 40,000, which is made possible using a scale of 'impurity', where a relaxed set of rules is used when a solution is not possible using strict rules. These solutions are obtained computationally. A PDF of the full results, or a quick ASCII file of the first 1000 can be downloaded.
Contributed solutions, using relatively simple rules.
Another program that can compute Four Fours solutions, and variants of the Four Four problem.
Provides more relaxed rules. Note that only the rules under the heading "Acceptable symbols and operators" are applicable to comp-sci's Four Fours.