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Search: id:A079667
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| A079667 |
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(1/2)*Sum_{d divides n} abs(n/d-d). |
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+0
5
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| 0, 1, 2, 3, 4, 6, 6, 9, 8, 12, 10, 16, 12, 18, 16, 21, 16, 27, 18, 28, 24, 30, 22, 40, 24, 36, 32, 42, 28, 50, 30, 49, 40, 48, 36, 65, 36, 54, 48, 66, 40, 72, 42, 70, 60, 66, 46, 92, 48, 77, 64, 84, 52, 96, 60, 92, 72, 84, 58, 126, 60, 90, 82, 105, 72, 120, 66, 112, 88, 114, 70
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Also, Sum{i|n, sqrt(n) < i <= n} i - Sumi|n, {1 <= i <sqrt(n)} i.
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REFERENCES
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H. J. S. Smith, Report on the Theory of Numbers, reprinted in Vol. 1 of his Collected Math. Papers, Chelsea, NY, 1979, see p. 323.
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FORMULA
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a(n) = A070038(n)-A066839(n).
G.f.: Sum_{k>0} x^(k^2+k)/(1-x^k)^2 . - Michael Somos Nov 19 2005
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PROGRAM
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(PARI) a(n)=if(n<2, 0, sumdiv(n, d, abs(n/d-d))/2) /* Michael Somos Nov 19 2005 */
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CROSSREFS
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Cf. A060866, A116589.
Sequence in context: A034298 A092404 A094871 this_sequence A073061 A006874 A034890
Adjacent sequences: A079664 A079665 A079666 this_sequence A079668 A079669 A079670
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 25 2003
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