The first and last numbers in each row are 1.

Every other number is formed by adding the two numbers just above that number in the previous row.

The expansion of has terms and the expansion of has  terms.

The coefficients for the expansion of come from the th row of Pascals triangle.

The coefficients for the expansion of come from the row above the th row of Pascals triangle.

The coefficients of the terms of the expansion of are all positive, whereas every second coefficient in the expansion of is negative.