Pascal's triangle

In Pascal's triangle, each number is the sum of the two numbers immediately above it, left and right - for example, 2 is the sum of 1 and 1, and 4 is the sum of 3 and 1. Furthermore, the sum of each row equals a power of 2 - for example, the sum of the 3rd row is 4 = 2²; the sum of the 4th row is 8 = 2³.

Triangular array of numbers (with 1 at the apex), in which each number is the sum of the pair of numbers above it. It is named after French mathematician Blaise Pascal, who used it in his study of probability. When plotted at equal distances along a horizontal axis, the numbers in the rows give the binomial probability distribution (with equal probability of success and failure) of an event, such as the result of tossing a coin.