A set of positive integers is called weakly -multiple-free if, for any integer , the set .
A set of positive integers is called strongly -multiple-free if implies , , ..., .
A set of positive integers is called weakly -multiple-free if, for any integer , the set .
A set of positive integers is called strongly -multiple-free if implies , , ..., .
Weisstein, Eric W. "Multiple-Free Set." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Multiple-FreeSet.html