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A076617
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Numbers n such that sum of the divisors d of n divides the sum of the non-divisors d' of n, where 1 <= d, d' <= n.
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0
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1, 2, 15, 20, 24, 95, 104, 207, 224, 287, 464, 1023, 1199, 1952, 4095, 4607, 8036, 12095, 15872, 16895, 19359, 22932, 23519, 28799, 45440, 45695, 54144, 77375
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| The sum of the divisors of 15 is sigma(15) = 24; the sum of the non-divisors of 15 that are between 1 and 15 is 2 + 4 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 = 96. Since 24 divides 96, 15 is a term of the sequence.
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MAPLE
| with(numtheory);
P:=proc(i)
local a, n;
for n from 1 to i do
a:=(n*(n+1))/(2*sigma(n))-1; if a=trunc(a) then print(n); fi;
od;
end:
P(10000000000); # Paolo P. Lava, Dec 12 2011
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MATHEMATICA
| a = {}; Do[ s = DivisorSigma[1, i]; n = (i (i + 1) / 2) - s; If[Mod[n, s] == 0, a = Append[a, i]], {i, 1, 10^5}]; a
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CROSSREFS
| Cf. A024816.
Sequence in context: A031022 A194542 A076646 * A091791 A143660 A198391
Adjacent sequences: A076614 A076615 A076616 * A076618 A076619 A076620
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 22 2002
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