A Set of Positive integers is double-free if, for any integer , the Set
(or equivalently, Implies ). Define
See also Triple-Free Set
References
Finch, S. ``Favorite Mathematical Constants.'' http://www.mathsoft.com/asolve/constant/triple/triple.html
Wang, E. T. H. ``On Double-Free Sets of Integers.'' Ars Combin. 28, 97-100, 1989.