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A postage problem. (English) Zbl 1250.97004

Summary: Let \(a\) and \(b\) be two positive integers greater than 1. Suppose that \(a\) and \(b\) are relatively prime. Then, there exists a positive integer \(N\) such that for all integers \(n\geq N\), there exist nonnegative integers \(x\) and \(y\) such that \(n = ax + by\). Furthermore, it is not possible to find nonnegative integers for \(x\) and \(y\) such that \(N -1=ax+by\).

MSC:

97F60 Number theory (educational aspects)
11D04 Linear Diophantine equations
97N70 Discrete mathematics (educational aspects)
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