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A206030
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Numbers m with at least two divisors d with the same sigma(d).
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3
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66, 132, 170, 198, 210, 260, 264, 322, 330, 340, 345, 396, 400, 420, 456, 462, 510, 520, 528, 594, 630, 644, 651, 660, 680, 690, 726, 780, 792, 800, 820, 840, 850, 858, 912, 924, 966, 990, 1020, 1035, 1040, 1050, 1056, 1066, 1092, 1122, 1155, 1160, 1188
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OFFSET
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1,1
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COMMENTS
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Complement of sequence contains numbers whose divisors d have distinct values of sigma(d).
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LINKS
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EXAMPLE
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66 is in sequence because two divisors d (6 and 11) of 66 have the same sigma(d) = 12.
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MATHEMATICA
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Select[Range[1200], Length[DivisorSigma[1, Divisors[#]]] != Length[Union[DivisorSigma[1, Divisors[#]]]] &] (* T. D. Noe, Feb 10 2012 *)
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PROG
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(PARI) ok(n)={my(v=apply(sigma, divisors(n))); #Set(v) < #v} \\ Andrew Howroyd, Aug 01 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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