A New Puzzle Challenges Math Skills
KenKen or KEN-KEN is a style of arithmetic and logical puzzle sharing several characteristics with sudoku. The name comes from Japanese and is translated as “square wisdom” or “cleverness squared”.
Related: list of logic puzzels
For online games, visit http://www.webkendoku.com where there are over 1000 random games in 4×4, 6×6, and 8×8 tables and difficulties like easy, medium, hard, and no-op.