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Search: id:A141115
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| A141115 |
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Those positive integers n where both d(d(n)) is not coprime to n and d(d(n)) does not divide n, where d(n) is the number of divisors of n. |
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+0
3
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| 18, 30, 42, 50, 54, 66, 70, 78, 98, 102, 110, 114, 130, 138, 140, 154, 160, 162, 170, 174, 182, 186, 190, 200, 220, 222, 224, 230, 238, 242, 246, 250, 258, 260, 266, 282, 286, 290, 308, 310, 315, 318, 322, 338, 340, 350, 352, 354, 364, 366, 370, 374, 380, 392
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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50 has 6 divisors and 6 has 4 divisors. 4 is not coprime to 50 and 4 does not divide 50. So 50 is in the sequence.
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MATHEMATICA
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Select[Range[400], GCD[DivisorSigma[0, DivisorSigma[0, # ]], # ] > 1 && Mod[ #, DivisorSigma[0, DivisorSigma[0, # ]]] > 0 &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 05 2008
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CROSSREFS
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Cf. A010553, A141113, A141114.
Sequence in context: A161164 A092357 A167515 this_sequence A039320 A043143 A043923
Adjacent sequences: A141112 A141113 A141114 this_sequence A141116 A141117 A141118
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jun 04 2008
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 05 2008
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