Early 2009, I read about KenKen (also known as Calcudoku) in the New York Times, and decided to write a program that creates similar puzzles, and put them online. Calcudoku puzzles are similar to Sudoku, but also require some basic math skills to solve. The rules are: the 4×4 puzzle uses the numbers 1-4, the 6×6 the numbers 1-6, and so on in each row and in each column each digit can appear only o