Syndetic set
In mathematics, a syndetic set is a subset of the natural numbers having the property of "bounded gaps": that the sizes of the gaps in the sequence of natural numbers is bounded. == Definition == A set S ⊂ N {\displaystyle S\subset \mathbb {N} } is called syndetic if for some finite subset F {\displaystyle F} of N {\displaystyle \mathbb {N} } ⋃ n ∈ F ( S − n ) = N {\displaystyle \bigcup _{n\in F}(S-n)=\mathbb {N} } where S − n = { m ∈ N : m + n ∈ S } {\displaystyle S-n=\{m\in \mathbb {N} :m+n\in S\}} .