Discovered by French mathematician Blaise Pascal in 1653. Every number in the interior of the triangle is the sum of the two numbers directly above it.

              01 
            01  01 
          01  02  01 
        01  03  03  01 
      01  04  06  04  01 
    01  05  10  10  05  01 
  01  06  15  20  15  06  01