Numble

Numble is a 1968 board game published by Selchow and Righter which is very similar to Scrabble. Instead of forming words, players form sequences adhering to certain arithmetic and numerical constraints.

Each tile in Numble has a single digit, 0 through 9, except for two blanks. A "word" in Numble is a string of digits in sequence (either ascending or descending). For example, 2,3,6,7 is a valid sequence (ascending), as is 7,6,3,2 (descending) while 3,6,7,1,1 (the same numbers) is not in sequence. The sum of the digits 1,1,3,6,7 is a multiple of 3. (7+6+3+2=18 and 18 is 6*3 a multiple of 3)