How to define the least common multiple

Answer 1

you can write a recusive function that returns the greatest common divisor using gcd(a,b)=gcd(a,b%a) and gcd(a,b)=gcd(b,a) and use the fact that a*b/gcd(a,b) = lcm(a,b)

Answer 2

https://en.m.wikipedia.org/wiki/Least_common_multiple