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A076525
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Numbers n such that sopf(n) = sopf(n+1) - sopf(n-1), where sopf(x) = sum of the distinct prime factors of x.
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8
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4, 22, 57, 900, 1551, 1920, 4194, 6279, 10857, 19648, 20384, 32016, 63656, 65703, 83271, 84119, 86241, 105570, 145237, 181844, 271328, 271741, 316710, 322953, 331976, 345185, 379659, 381430, 409915, 424503, 490255, 524476, 542565, 550271
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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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The sum of the distinct prime factors of 22 is 2 + 11 = 13; the sum of the distinct prime factors of 23 is 23; the sum of the distinct prime factors of 21 is 3 + 7 = 10; and 13 = 23 - 10. Hence 22 belongs to the sequence.
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MATHEMATICA
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p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^5], p[ # ] == p[ # + 1] - p[ # - 1] &]
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PROG
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(Magma) [k:k in [3..560000]| &+PrimeDivisors(k) eq &+PrimeDivisors(k+1)-&+PrimeDivisors(k-1)]; // Marius A. Burtea, Oct 10 2019
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CROSSREFS
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KEYWORD
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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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