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Search: id:A075997
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| A075997 |
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a(n)=[n/2]-[n/3]+[n/4]-[n/5]+[n/6]-..., where [n/k]=Floor(n/k). |
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+0
2
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| 0, 0, 1, 0, 2, 1, 2, 1, 4, 2, 3, 2, 5, 4, 5, 2, 6, 5, 6, 5, 8, 5, 6, 5, 10, 8, 9, 6, 9, 8, 9, 8, 13, 10, 11, 8, 12, 11, 12, 9, 14, 13, 14, 13, 16, 11, 12, 11, 18, 16, 17, 14, 17, 16, 17, 14, 19, 16, 17, 16, 21, 20, 21, 16, 22, 19, 20, 19, 22, 19, 20, 19, 26, 25, 26, 21, 24, 21, 22, 21
(list; graph; listen)
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OFFSET
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0,5
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FORMULA
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a(n)= n-A006218(n)+2*A006218(floor(n/2)). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Oct 02 2002
a(n) = n - sum{n/2<k<=n} d(k) + sum{1<=k<=n/2} d(k), where d(k) = A000005(k). Also, a(n) = number of terms among {floor(n/k)}, 1<=k<=n, which are even. - Leroy Quet (qq-quet(AT)mindspring.com), Jan 19 2006
G.f.: Sum(x^(2*i)/(1+x^i),i=1..infinity)/(1-x). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Apr 24 2006
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EXAMPLE
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a(6) = [6/2]-[6/3]+[6/4]-[6/5]+[6/6]-[6/7]+... = 3-2+1-1+1-0+... = 2.
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CROSSREFS
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a(n)=n-A059851(n).
Cf. A060831.
Sequence in context: A050363 A111588 A070972 this_sequence A029196 A051493 A029173
Adjacent sequences: A075994 A075995 A075996 this_sequence A075998 A075999 A076000
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), Sep 28 2002
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