Pascal's triangle is an arrangement of numbers described by Pascal in his Traité du Triangle Arithmétique published in the year 1665 as 'The number in each cell is equal to in the preceding cell in the same column plus that in the preceding cell in the same row'. He placed arbitrary number in the first cell (in the right angle of triangle) and regarded the construction of the first row and column as special 'because their cells do not have any cells preceding them'. Supposing the number in the first cell to be unity then the arrangement produces.
More generally nowadays the numbers would be arranged as shown follows;