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A144967
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Semiprimes n such that n + 1 is divisible by the sum of decimal digits of n.
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2
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10, 14, 34, 65, 143, 215, 299, 362, 454, 458, 545, 655, 671, 689, 799, 917, 922, 923, 943, 1003, 1007, 1042, 1055, 1111, 1154, 1199, 1253, 1273, 1379, 1507, 1529, 1739, 1807, 1835, 1919, 1957, 2045, 2095, 2183, 2209, 2231, 2279, 2302, 2326, 2342, 2435
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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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14 and 15 are semiprimes. 14+1 = 15 is divisible by 1+4 = 5, hence 14 is in the sequence; 15+1 = 16 is not divisible by 1+5 = 6, hence 15 is not in the sequence. - Klaus Brockhaus, Sep 29 2008
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MATHEMATICA
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Select[Range[5000], Sum[FactorInteger[ # ][[i, 2]], {i, 1, Length[FactorInteger[ # ]]}] == 2 && Mod[ # + 1, Plus @@ IntegerDigits[ # ]] == 0 &] (* Stefan Steinerberger, Sep 29 2008 *)
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CROSSREFS
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KEYWORD
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base,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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