The scoring system for tile matching is usually nonlinear to reward a player's efforts to catch long sequences of tiles. There is no specific rule or formula for that; game developers can design expressions for themselves.

The following is a chart showing one of the examples of a score formula (you can develop your own score principles) based on arithmetic progression steps:

In general, various forms of progressions may be used. For example, an arithmetic progression gives a smooth and comfortable increase in values, but geometric progression is sharper and returns larger numbers.