Published online by Cambridge University Press: 26 February 2010
A sequence {an} of integers is said to be primitive if whenever i ≠ j. For example, if n is any positive integer, the sequence
is primitive. This is an important example in the light of the elementary result (see [2; p. 244]) that if 0 < a1 < a2 < … < ar ≤ 2n is primitive then necessarily r ≤ n; i.e. at most half of the positive integers ≤ 2n can be members of the sequence. Besicovitch [2; p. 257] has obtained the surprising result that, given ε > 0, there exists an infinite primitive sequence {ai} such that
where A(n) denotes the number of ai ≤ n.