what is the sum of the squares of the first 20 natural numbers ( 1 to 20 ) ?
n ( n + 1 ) ( 2 n + 1 ) / 6 20 ( 21 ) ( 21 ) / 6 = 2870 answer : a
divide(multiply(multiply(20, add(20, 1)), add(multiply(const_2, 20), 1)), multiply(const_2, const_3))