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A258077
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Numbers x such that (-1)sigma(x) | sigma(x), where (-1)sigma(x) is defined in A049060 and sigma(x) is the sum of the divisors of x (A000203).
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2
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1, 2, 3, 6, 14, 15, 30, 35, 42, 70, 78, 105, 190, 210, 348, 357, 418, 570, 714, 812, 910, 1045, 1254, 2090, 2436, 2730, 3135, 4060, 4522, 4674, 5278, 6270, 9990, 10659, 12180, 12441, 13566, 14630, 15834, 16770, 20026, 21318, 21978, 23374, 24244, 24871, 24882
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listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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Paolo P. Lava, Table of n, a(n) for n = 1..100
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EXAMPLE
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(-1)sigma(1) = 1, sigma(1) = 1 and 1 / 1 = 1;
(-1)sigma(2) = 1, sigma(2) = 3 and 3 / 1 = 3;
(-1)sigma(35) = 24, sigma(35) = 48 and 48 / 24 = 2; etc.
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MAPLE
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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)/b, integer) then print(n); fi; od; end: P(10^6);
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CROSSREFS
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Cf. A000203, A049060, A258079.
Sequence in context: A134737 A030733 A122839 * A121556 A123041 A078557
Adjacent sequences: A258074 A258075 A258076 * A258078 A258079 A258080
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KEYWORD
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nonn
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AUTHOR
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Paolo P. Lava, May 19 2015
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STATUS
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approved
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