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A015709
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Composite n such that phi(n) * sigma(n) is one less than a square.
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3
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6, 22, 33, 44, 69, 76, 82, 140, 190, 295, 354, 392, 423, 451, 531, 581, 650, 944, 1072, 1119, 1142, 1150, 1668, 2276, 2893, 4043, 4163, 4176, 4192, 4257, 4262, 4509, 5090, 5975, 7260, 8660, 12977, 14927, 15026, 15753, 16064, 19105
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OFFSET
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1,1
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LINKS
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PROG
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(PARI) isok(n) = !isprime(n) && issquare(eulerphi(n)*sigma(n)+1); \\ Michel Marcus, Oct 02 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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