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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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7
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 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
| p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^5], p[ # ] == p[ # + 1] - p[ # - 1] &]
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CROSSREFS
| Cf. A008472, A075565, A075784, A075846, A076527, A076531, A076532, A076533.
Sequence in context: A022603 A050773 A122241 * A089761 A098837 A104171
Adjacent sequences: A076522 A076523 A076524 * A076526 A076527 A076528
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 18 2002
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EXTENSIONS
| Edited and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 13 2005
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