Abaku

From BoardGameGeek:

Abaku is a crossword-style tile-placement game for 1-4 players. Players place number tiles horizontally or vertically to create intersecting arithmetic equations. Operation signs and equals signs are not placed on the board; the mathematical relationships are read directly from the sequence of digits. For example, 112 can represent 1 + 1 = 2, while 248 can represent 2 × 4 = 8. On each turn, a player adds one or more tiles to the existing layout. Every new sequence created by the placement must form a valid equation. The game uses addition, subtraction, multiplication, division, squares, cubes, square roots, and cube roots with whole numbers. Players score all valid equations created during their turn. Premium spaces can increase the value of tiles or completed equations. The player with the highest score wins. Abaku was first published as a board game in 2008. It is also available as an online multiplayer game and has been played online continuously since 2009.