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A055719
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d(n)-1 | n and n is not prime.
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3
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4, 6, 15, 16, 20, 21, 27, 33, 39, 42, 45, 50, 51, 56, 57, 69, 70, 75, 87, 93, 105, 111, 120, 123, 129, 132, 141, 154, 159, 162, 175, 177, 182, 183, 189, 198, 201, 210, 213, 219, 220, 231, 237, 238, 245, 249, 256, 266, 267, 270, 273, 275, 291, 303, 308, 309, 321
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OFFSET
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1,1
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COMMENTS
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Composite integers divisible by 1 less than the number of their divisors.
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LINKS
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MATHEMATICA
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Do[ If[ !PrimeQ[ n ], If[ IntegerQ[ n/(DivisorSigma[ 0, n ]-1) ], Print[ n ] ] ], {n, 1, 500} ]
Select[Range[2, 400], !PrimeQ[#]&&Divisible[#, DivisorSigma[0, #]-1]&] (* Harvey P. Dale, Mar 13 2013 *)
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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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