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Search: id:A130871
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| A130871 |
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Numbers n such that the sum of the prime factors with multiplicity of n divides n+1. |
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+0
2
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| 15, 35, 44, 54, 90, 95, 119, 143, 209, 287, 319, 323, 328, 351, 377, 390, 423, 527, 559, 608, 779, 899, 923, 924, 989, 1007, 1189, 1199, 1280, 1343, 1349, 1715, 1763, 1805, 1825, 1919, 2000, 2159, 2448, 2507, 2755, 2759, 2847, 2911, 3008
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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List the factors of n with multiplicity to see if their sum divides the following number n+1.
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EXAMPLE
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90=2*3*3*5 with sum 2+3+3+5=13, 7*13=91, so 90 is in the sequence.
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MATHEMATICA
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Select[Range[2, 10000], IntegerQ[(# + 1)/Sum[FactorInteger[ # ][[i, 1]] *FactorInteger[ # ][[i, 2]], {i, 1, Length[FactorInteger[ # ]]}]] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 26 2007
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CROSSREFS
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Sequence in context: A134335 A080774 A114988 this_sequence A108668 A063532 A090196
Adjacent sequences: A130868 A130869 A130870 this_sequence A130872 A130873 A130874
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KEYWORD
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easy,nonn
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AUTHOR
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J. M. Bergot (thekingfishb(AT)yahoo.ca), Jul 24 2007
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EXTENSIONS
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Corrected and extended by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 26 2007
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