Pascal’s triangle can be described as an quilateral triangle.  It is bordered by 1′s going down the right and left sides of the triangle.  The second row of diagonals are counting numbers 1,2,3,….  The interior triangles are created by the sum of the two numbers above.  Each row starts and ends with the number 1.  If you folded the triangle symmetrically, every odd row would match.  Looking at the apex and down, the numbers are increasing.