lcm returns the least common multiple of the integers.
If no integer is supplied, the integer 1 is returned.
If only one integer is supplied,
the absolute value of that integer is returned.
For two arguments that are not both zero,
(lcm a b) ==(/ (abs (* a b)) (gcd a b))
If one or both arguments are zero,
(lcm a 0) ==(lcm 0 a) ==0
For three or more arguments,
(lcm a b c ... z) ==(lcm (lcm a b) c ... z)