The sum of the first n positive integers 1 + 2 + 3 + …+ n = Σk and the sum of the first n squares 1 +2 + 3 + …+ n = Σk2 arise in several middle school and high school mathematics problems—for example, in the handshake and cannonball problems (e.g., Driscoll 1999). The solutions involve familiar formulas expressing each sum as a function of n: