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A068978
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Numbers k such that Sum_{d|k} tau(d)/d is an integer, where tau(x) = A000005(x).
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7
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1, 2, 9, 18, 105, 210, 24375, 48750, 133848, 18780741, 18780965, 37561482, 37561930, 121486365, 169028685, 242972730, 338057370, 360988056, 676114740, 1120584213, 1285201500, 1352229480, 2241168426, 2776831200, 5352575025, 5408917920, 7437262140, 10705150050
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OFFSET
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1,2
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COMMENTS
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Also k such that k divides A007429(k).
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LINKS
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MATHEMATICA
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t = {}; n = 0; While[n++ <= 20000000, If[Mod[Total[DivisorSigma[1, Divisors[n]]], n] == 0, AppendTo[t, n]]]; t (* Jayanta Basu, Apr 03 2013 *)
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PROG
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(PARI) for(n=1, 20000000, if(denominator( sumdiv(n, d, numdiv(d)/d)) ==1, print1(n, ", ")))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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