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Search: id:A071324
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| A071324 |
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Alternating sum of all divisors of n; divisors non-increasing, starting with n. |
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+0
7
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| 1, 1, 2, 3, 4, 4, 6, 5, 7, 6, 10, 8, 12, 8, 12, 11, 16, 13, 18, 12, 16, 12, 22, 16, 21, 14, 20, 18, 28, 22, 30, 21, 24, 18, 32, 25, 36, 20, 28, 24, 40, 32, 42, 30, 36, 24, 46, 32, 43, 31, 36, 36, 52, 40, 48, 38, 40, 30, 58, 40, 60, 32, 46, 43, 56, 48, 66, 48, 48, 42, 70, 49, 72
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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a(A028983(n)) mod 2 = 0; a(A028982(n)) mod 2 = 1.
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LINKS
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R. Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
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Equals A054525 * A134871; i.e. Mobius transform of [1, 2, 3, 5, 5, 8, 7, 10, 10, 12, 11,...]. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Nov 14 2007
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EXAMPLE
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Divisors of 20: {1,2,4,5,10,20} therefore a(20) = 20-10+5-4+2-1 = 12.
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CROSSREFS
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Cf. A000203, A071322, a(n)=abs(A071323(n)).
Cf. A134871.
Sequence in context: A008328 A091860 A071323 this_sequence A063655 A117248 A079788
Adjacent sequences: A071321 A071322 A071323 this_sequence A071325 A071326 A071327
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), May 18 2002, Jul 03 2008
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