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 A291258 a(n) is the smallest number k such that sigma(k) - phi(k) = n*k, or 0 if no such k exists. 0
 1, 2, 12, 75960, 17156160 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(5) and following terms > 10^13, if they exist. - Giovanni Resta, Aug 21 2017 LINKS EXAMPLE 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. PROG (PARI) a(n) = {my(k=1); while (sigma(k)-eulerphi(k)!=n*k, k++); k; } CROSSREFS Cf. A000010, A000203, A055681. Sequence in context: A280734 A048830 A038081 * A027737 A063970 A130769 Adjacent sequences:  A291255 A291256 A291257 * A291259 A291260 A291261 KEYWORD nonn,more AUTHOR Altug Alkan, Aug 21 2017 STATUS approved

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Last modified May 25 01:28 EDT 2019. Contains 323534 sequences. (Running on oeis4.)