According to Van der Waerden, the sum of two natural numbers is defined as
&x*1=x&
&x*y^+= x*y+x& (for every x and every y)
The product of two natural numbers is recursively defined as
&x*1=x&
&x*y^+= x*y+x& (for every x and every y)
x^+ ( y^+ ) here means the successor(consequent) of x( y) in the set of natural numbers.