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A291258
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a(n) is the smallest number k such that sigma(k) - phi(k) = n*k, or 0 if no such k exists.
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0
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OFFSET
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0,2
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COMMENTS
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a(5) and following terms > 10^13, if they exist. - Giovanni Resta, Aug 21 2017
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LINKS
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EXAMPLE
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a(2) = 12 because sigma(12) = 28, phi(12) = 4; sigma(12) - phi(12) = 2*12 and 12 is the smallest number with this property.
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PROG
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(PARI) a(n) = {my(k=1); while (sigma(k)-eulerphi(k)!=n*k, k++); k; }
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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