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A370354
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Composite numbers k that share a factor with sopfr(k), the sum of the primes dividing k, with repetition.
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2
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4, 8, 9, 16, 18, 24, 25, 27, 30, 32, 36, 42, 49, 50, 60, 64, 66, 70, 72, 78, 81, 84, 98, 100, 102, 105, 110, 114, 120, 121, 125, 126, 128, 130, 132, 138, 140, 144, 150, 154, 156, 160, 162, 168, 169, 170, 174, 180, 182, 186, 190, 192, 195, 196, 200, 204, 216, 220, 222, 228, 230, 231, 234, 238, 240
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OFFSET
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1,1
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COMMENTS
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All prime powers, see A246547, are terms.
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LINKS
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EXAMPLE
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18 is a term as 18 = 2 * 3 * 3, and soprf(18) = 2 + 3 + 3 = 8, which shares a factor with 18.
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MATHEMATICA
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fn[{a_, b_}]:=a*b; Select[Range[240], CompositeQ[#]&&ContainsAny[First/@FactorInteger[#], First/@FactorInteger[ Total[fn/@FactorInteger[#]]]]&] (* James C. McMahon, May 06 2024 *)
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CROSSREFS
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KEYWORD
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nonn,new
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AUTHOR
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STATUS
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approved
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