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A062680
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Composite numbers whose divisors (except 1) all contain the digit 9.
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18
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1691, 2291, 3629, 5191, 5539, 5597, 6931, 7391, 7921, 7961, 8497, 8791, 9101, 9329, 9409, 9481, 9671, 9701, 10981, 10991, 11269, 13129, 13891, 14239, 15089, 15931, 15941, 16999, 17197, 17309, 17879, 17951, 17993, 18091, 18449, 18829, 18943
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OFFSET
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1,1
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LINKS
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EXAMPLE
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7961 has divisors 19, 419 and 7961, all of which contain the digit 9.
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MATHEMATICA
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fQ[n_] := Union[Drop[Last /@ Sort /@ IntegerDigits[ Divisors[ n]], 1]] == {9}; Select[ Range[ 19110], fQ[ # ] == True && ! PrimeQ[ # ] &] (* Zak Seidov and Robert G. Wilson v, May 17 2005 *)
fQ[n_, dgt_] := Union[ MemberQ[#, dgt] & /@ IntegerDigits@ Rest@ Divisors@ n][[1]]; Select[ Range[2, 19110], !PrimeQ[#] && fQ[#, 9] &] (* Robert G. Wilson v, Jun 11 2014 *)
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PROG
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(Magma) [k:k in [2..20000]| not IsPrime(k) and forall{d:d in Set(Divisors(k)) diff {1}| 9 in Intseq(d)}]; // Marius A. Burtea, Nov 07 2019
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CROSSREFS
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Cf. A062653, A062664, A062667, A062668, A062669, A062670, A062671, A062672, A062673, A062674, A062675, A062676, A062677, A062678.
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KEYWORD
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base,easy,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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