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 A258079 Numbers x such that (-1)sigma(x) | sigma(x) - x, where (-1)sigma(x) is defined in A049060 and sigma(x) - x is the sum of the aliquot parts of x (A001065). 1
 1, 2, 6, 10, 36, 168, 1098, 1204, 2840, 19488, 1881124, 3105700, 445577184, 105314212224, 134633963520, 2167649138304 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Ratio is equal to 1 for 2, 36, 1204, 2840, 1881124, 3105700, ... a(17) > 10^13. - Hiroaki Yamanouchi, Sep 11 2015 LINKS EXAMPLE (-1)sigma(1) = 1, sigma(1) - 1 = 1 - 1 = 0 and 0 / 1 = 0; (-1)sigma(2) = 1, sigma(2) - 2 = 3 - 2 = 1 and 1 / 1 = 1; (-1)sigma(36) = 55, sigma(36) - 36 = 91 - 36 = 55 and 55 / 55 = 1; etc. MAPLE with(numtheory): P:=proc(q) local a, b, i, j, n; for n from 1 to q do a:=ifactors(n)[2]: b:=1; for i from 1 to nops(a) do b:=b*(-1+sum(a[i][1]^j, j=1..a[i][2])): od: if type((sigma(n)-n)/b, integer) then print(n); fi; od; end: P(10^6); CROSSREFS Cf. A001065, A049060, A258077. Sequence in context: A218965 A248821 A260559 * A027165 A111414 A202533 Adjacent sequences:  A258076 A258077 A258078 * A258080 A258081 A258082 KEYWORD nonn,more AUTHOR Paolo P. Lava, May 19 2015 EXTENSIONS a(13)-a(16) from Hiroaki Yamanouchi, Sep 11 2015 STATUS approved

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Last modified April 19 16:58 EDT 2019. Contains 322283 sequences. (Running on oeis4.)