Enumerating possible Sudoku grids Bertram Felgenhauer Department of Computer Science TU Dresden 01069 Dresden Germany bf3@mail.inf.tu-dresden.de Frazer Jarvis Department of Pure Mathematics University of Sheffield, Sheffield S3 7RH, U.K. a.f.jarvis@shef.ac.uk June 20, 2005 Introduction Sudoku puzzles became extremely popular in Britain from late-2004. Sudoku, or Su Doku, is a Japanese word (or phrase) meaning something like Number Place. The idea of the puzzle is extremely simple; the solver is faced with a 9 × 9 grid, divided into nine 3 × 3 blocks: In some of these boxes, the setter puts some of the digits 1–9; the aim of the solver is to complete the grid by filling in a digit in every box in such a way that each row, each column, and each 3 × 3 box contains each of the digits 1–9 exactly once. In this note, we discuss the problem of enumerating all possible Sudoku grids. This is a very natural problem, but, perhaps surprisingly, it seems unlikely that the proble
