Definition:Pascal's Triangle

Pascal's Triangle is an array formed by the binomial coefficients:

$$\begin{array}{r|rrrrrrrrrr} n & \binom n 0 & \binom n 1 & \binom n 2 & \binom n 3 & \binom n 4 & \binom n 5 & \binom n 6 & \binom n 7 & \binom n 8 & \binom n 9 \\ [4pt] \hline 0 & 1 & 0 & 0 &  0 &   0 &   0 &  0 &  0 & 0 & 0 \\ 1 & 1 & 1 &  0 &  0 &   0 &   0 &  0 &  0 & 0 & 0 \\ 2 & 1 & 2 &  1 &  0 &   0 &   0 &  0 &  0 & 0 & 0 \\ 3 & 1 & 3 &  3 &  1 &   0 &   0 &  0 &  0 & 0 & 0 \\ 4 & 1 & 4 &  6 &  4 &   1 &   0 &  0 &  0 & 0 & 0 \\ 5 & 1 & 5 & 10 & 10 &   5 &   1 &  0 &  0 & 0 & 0 \\ 6 & 1 & 6 & 15 & 20 &  15 &   6 &  1 &  0 & 0 & 0 \\ 7 & 1 & 7 & 21 & 35 &  35 &  21 &  7 &  1 & 0 & 0 \\ 8 & 1 & 8 & 28 & 56 &  70 &  56 & 28 &  8 & 1 & 0 \\ 9 & 1 & 9 & 36 & 84 & 126 & 126 & 84 & 36 & 9 & 1 \\ \end{array}$$

Also see

 * Pascal's Rule
 * Stirling's Triangles

Historical Note
The earliest reference to it seems to date from between the 5th and 2nd centuries B.C.E. by the Hindu writer Pingala.

In Iran it is known as the Khayyam Triangle after Omar Khayyám discussed it in ca. 1100 C.E. It had been discussed even before that by al-Karajī a hundred years previously.

In India it was discussed at length by Bhāskara II Āchārya in his ca. 1150 work Līlāvatī.

In China it is known as Yang Hui's Triangle after Yang Hui, who himself (in 1261) credited it to Chia Hsien in a work (ca. 1000 C.E.) now lost.

The first record of it in Europe seems to be when Petrus Apianus published it on the frontispiece of his book on business calculations in the 16th century.

It is also known (particularly in Italy) as Tartaglia's Triangle, after Niccolò Fontana Tartaglia.

It was Pascal's 1653 treatise Traité du triangle arithmétique which was perhaps the first time the main properties of this triangle were documented in one place.

The name Pascal's Triangle was assigned by Pierre Raymond de Montmort in 1708, and Abraham de Moivre in 1730.