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A015705
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Geometric mean of phi(n) and sigma(n) is an integer, n odd.
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1
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1, 51, 105, 405, 477, 595, 679, 1023, 1455, 1463, 1485, 1715, 1731, 2651, 2945, 3135, 3567, 4381, 5797, 5859, 8245, 8255, 8721, 9639, 9809, 10127, 10153, 10179, 10295, 11935, 12369, 17765, 17955, 19125, 19875, 20195, 20213, 20273
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OFFSET
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1,2
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LINKS
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PROG
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(PARI) isok(n) = (n%2) && issquare(sigma(n)*eulerphi(n)); \\ 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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