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A049642
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Number of divisors of n does not divide sum of divisors of n.
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6
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2, 4, 8, 9, 10, 12, 16, 18, 24, 25, 26, 28, 32, 34, 36, 40, 48, 50, 52, 58, 63, 64, 72, 74, 75, 76, 80, 81, 82, 84, 88, 90, 98, 100, 104, 106, 108, 112, 117, 120, 121, 122, 124, 128, 130, 136, 144, 146, 148, 152, 156, 160, 162, 170, 171, 172, 175
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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A054025(a(n)) > 0. [Reinhard Zumkeller, Jan 06 2012]
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REFERENCES
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Handbook of Number Theory, D. S. Mitrinovic et al., Kluwer, Section III.51.
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LINKS
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Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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MAPLE
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with(numtheory);
A049642:=proc(q)
local a, b, c, i, n;
for n from 1 to q do
a:=divisors(n); b:=nops(a); c:=0; for i from 1 to b do c:=c+a[i]; od;
if trunc(c/b)<>c/b then print(n); fi; od; end:
A049642(1000); # Paolo P. Lava, Oct 26 2012
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MATHEMATICA
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Select[Range[175], Mod[DivisorSigma[1, #], DivisorSigma[0, #]] > 0 &] (* Jayanta Basu, Mar 28 2013 *)
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PROG
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(Haskell)
import Data.List (findIndices)
a049642 n = a049642_list !! (n-1)
a049642_list = map (+ 1) $ findIndices (> 0) a054025_list
-- Reinhard Zumkeller, Jan 06 2012
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CROSSREFS
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Complement of A003601.
Cf. A000005, A000203.
Sequence in context: A047466 A003485 A072602 * A050907 A100675 A196730
Adjacent sequences: A049639 A049640 A049641 * A049643 A049644 A049645
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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