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A257843
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Numbers n for which the lexicographically first integer solution (x,y,z) of 4/n = 1/x + 1/y + 1/z with 0 < x < y < z, is different from the solution having the largest z-value.
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3
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89, 113, 161, 233, 281, 329, 353, 401, 409, 449, 473, 521, 593, 641, 689, 713, 761, 769, 809, 929, 953, 1049, 1073, 1121, 1129, 1169, 1193, 1241, 1249, 1313, 1321, 1361, 1369, 1409, 1433, 1481, 1513, 1529, 1553, 1561, 1601, 1609, 1649, 1673, 1721, 1769
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OFFSET
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1,1
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COMMENTS
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Related to the Erdős-Straus conjecture, see A073101 for more details.
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LINKS
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EXAMPLE
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For n=89, 4/89 = 1/23 + 1/690 + 1/61410 = 1/24 + 1/306 + 1/108936 are the representations with the largest resp. smallest unit fraction.
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PROG
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(PARI) is(n, s=0)=for(c=n\4+1, n*3\4, for(b=c+1, ceil(2/(t=4/n-1/c))-1, numerator(t-1/b)==1||next; !s&&(s=t-1/b)&&next(2); t-1/b<s&&return(1)))
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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