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A036302
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Composite numbers k such that the digits of the prime factors of k are either 1 or 2.
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25
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4, 8, 16, 22, 32, 44, 64, 88, 121, 128, 176, 242, 256, 352, 422, 484, 512, 704, 844, 968, 1024, 1331, 1408, 1688, 1936, 2048, 2321, 2662, 2816, 3376, 3872, 4096, 4222, 4442, 4642, 5324, 5632, 6752, 7744, 8192, 8444, 8884, 9284, 10648, 11264, 13504, 14641, 15488, 16384
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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422 = 2 * 211 is in the sequence as the digits of its prime factors 2 and 211 are either 1 or 2. - David A. Corneth, Sep 26 2020
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MATHEMATICA
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Select[Range[2, 14650], !PrimeQ[#] && Complement[Flatten[IntegerDigits[First/@FactorInteger[#]]], {1, 2}]=={} &] (* Jayanta Basu, May 25 2013 *)
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PROG
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(Magma) [k:k in [2..15000]| not IsPrime(k) and forall{a: a in PrimeDivisors(k)|Intseq(a) subset {1, 2}}]; // Marius A. Burtea, Oct 08 2019
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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