40. Memorize the 1st 100 digits of the pi constant
The constant p (Greek letter pi) is, classically, defined as the ratio of the circumference of a circle to its diameter. This constant, among thousands of constants in the math world, interests me the most because over a several millenia, since the beginning of human civilisation, it has undergone refinements-an evolution of its own.
The first 42 digits are:
3.141592653589793238462643383279502884197