Perfect rulerA perfect ruler of length is a ruler with integer markings , for which there exists an integer such that any positive integer is uniquely expressed as the difference for some . This is referred to as an -perfect ruler. An optimal perfect ruler is one of the smallest length for fixed values of and . ExampleA 4-perfect ruler of length is given by . To verify this, we need to show that every positive integer is uniquely expressed as the difference of two markings: See alsoThis article incorporates material from perfect ruler on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.
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