We are given the set M={−22022,−22021,...,−22,−2,−1,1,2,22,...,22021,22022}.
Let T be a subset of M, such that neighbouring numbers have the same difference when the elements are ordered by size.
(a) Determine the maximum number of elements that such a set T can contain.
(b) Determine all sets T with the maximum number of elements.(Walther Janous) combinatoricsnumber theory