Traditionally, the elements of the Pascal Triangle are numbered for each row and place in the row. Both the row numbers and the place numbers start from 0. Here are the row numbers for a Pascal triangle. Note that in row 0, there is only 1 place, place 0, and its value is 1. Now we consider putting the elements in an array named a. Below the Pascal triangle are the names of the equivalent array elements.

Now consider how to give the definition of the array a so that it holds the Pascal numbers.

For all rows i (0 < i < R)
   and for all places j ( 0 < j <= i ),   
      if ( j = 0 )  then a(i,j) = . . .
        else if    . . .