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A181597
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(N\{4})-perfect numbers, i.e., numbers m for which sigma(m)-4 = 2m, if 4|m, otherwise sigma(m) = 2m.
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2
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OFFSET
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1,1
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COMMENTS
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Or union of {6}, near-perfect numbers m (cf. A181595) for which d(m)=4, and all odd perfect numbers (if they exist). Note that (N\{2})-perfect numbers are numbers for which sigma(m)-2=2m, if m is even, and sigma(m)=2m, if m is odd. They are all even numbers of A045768 and all odd perfect numbers (if they exist).
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LINKS
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Table of n, a(n) for n=1..10.
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EXAMPLE
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88 is in the sequence since sigma(88) = 180 and 180 - 4 = 2*88.
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CROSSREFS
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Cf. A000396, A005101, A005820, A088832, A118372, A153501, A181595, A181596.
Sequence in context: A054883 A005402 A128953 * A002898 A003613 A099767
Adjacent sequences: A181594 A181595 A181596 * A181598 A181599 A181600
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KEYWORD
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nonn,more
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AUTHOR
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Vladimir Shevelev, Nov 01 2010, Nov 03 2010
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EXTENSIONS
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Invalid term removed and a(8)-a(10) from Donovan Johnson, Sep 14 2013
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STATUS
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approved
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