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A240775
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The six values n in each interval [i*840, (i+1)*840), where i >= 0, for which Mordell's formulas do NOT provide a three-Egyptian-fraction solution for 4/n.
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1
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OFFSET
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1,2
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COMMENTS
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Erdős and Straus conjectured that for all integers n >= 2, the rational number 4/n can be expressed as an Egyptian fraction with exactly three unit fractions -- that is, 4/n = 1/x + 1/y + 1/z where x, y and z are positive integers. The conjecture has been verified to high values of n, and Mordell has provided formulas to compute x, y and z for many n. The values of n NOT included in Mordell's formulas are those for which n modulo 840 = {an element of this sequence}. Each element is the square of a prime.
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REFERENCES
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Louis J. Mordell, Diophantine Equations, Academic Press, 1967, 287-290.
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LINKS
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CROSSREFS
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KEYWORD
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nonn,fini,full
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AUTHOR
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STATUS
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approved
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