J Austral Math Soc Ser A 47 pp84--89, 1989.
(Received 23 November 1987)
We say that a positive integer d has property (A) if for all positive integers m there is an integer x, depending on m, such that, setting n = m + d, x lies between m and n and x is co-prime to mn. We show that infinitely many even d and infinitely many odd d have property (A). We conjecture and provide supporting evidence that all odd d have property (A). Following A. R. Woods [3] we describe conditions (Au) (for each u) asserting, for a given d, the existnece of a chain of at most u + 2 integers, each co-prime to its neighbours, which start with m and increase, finishing at n = m + d. Property (A) is equivalent to condition (A1), and it is easily shown that property (Ai) implies property (Ai+1). Woods showed that for some u all d have property (Au), and we conjecture and provide supporting evidence that the least such u is 2.
1980 AMS Subject Classification (1985 Revision): 11A05
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