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Search: id:A066176
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| A066176 |
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Numbers n such that sigma(n+1)-sigma(n) = sigma(n)/d(n), where d(n) denotes the number of divisors of n. |
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1
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| 135, 147, 189, 753, 2697, 8365, 14577, 16929, 18573, 21093, 38481, 67461, 69285, 99237, 100497, 108134, 144555, 148173, 186081, 253761, 263906, 302589, 536834, 560733, 680043, 1158717, 1239554, 1418121, 1431861, 1520313, 1545255, 1657077
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OFFSET
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1,1
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COMMENT
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These are the numbers n at which the divisor sum sigma(n) is increasing at a rate equal to the average divisor size, sigma(n)/d(n).
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EXAMPLE
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sigma(136)-sigma(135) = 270-240 = 30 = 240/8 = sigma(135)/d(135).
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MATHEMATICA
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Select[ Range[ 1, 10^5 ], DivisorSigma[ 1, #+1 ]-DivisorSigma[ 1, # ]==DivisorSigma[ 1, # ]/DivisorSigma[ 0, # ] & ]
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CROSSREFS
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Sequence in context: A007251 A038369 A066282 this_sequence A025363 A096593 A050215
Adjacent sequences: A066173 A066174 A066175 this_sequence A066177 A066178 A066179
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 14 2001
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EXTENSIONS
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More terms from Robert Gerbicz (robert.gerbicz(AT)gmail.com), Aug 21 2006
Corrected by T. D. Noe (noe(AT)sspectra.com), Oct 25 2006
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