Pascal's Triangle

In every arithmetical triangle all the cells of the first parallel row and of the first perpendicular row are the same as the generating cell.

For by definition each cell of the triangle is equal to the sum of the immediately preceding perpendicular and parallel cells. But the cells of the first parallel row have no preceding perpendicular cells, and those of the first perpendicular row have no preceding parallel cells; therefore they are all equal to each other and consequently to the generating number.

And similarly of the rest.