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Search: id:A070817
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| A070817 |
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Floor[n/2]-P[Phi[n]], where P(n) is the largest prime factor of n. |
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+0
1
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| -1, 0, 0, 1, 0, 2, 1, 3, 0, 4, 3, 4, 5, 6, 6, 6, 6, 8, 7, 6, 0, 10, 7, 10, 10, 11, 7, 13, 10, 14, 11, 15, 14, 15, 15, 16, 16, 18, 15, 18, 14, 17, 19, 12, 0, 22, 17, 20, 23, 23, 13, 24, 22, 25, 25, 22, 0, 28, 25, 26, 28, 30, 29, 28, 22, 32, 23, 32, 28, 33, 33, 34, 32, 35, 33, 36, 26, 38, 37, 36, 0, 39, 40, 36, 36, 39, 33, 42, 42, 35, 41, 24
(list; graph; listen)
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OFFSET
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3,6
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FORMULA
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a(n)=A004526(n)-A068211(n)=A004526(n)-A006530[A000010(n)]
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EXAMPLE
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n=3: Floor[3/2]=1,Phi[3]=2,P[2]=2, a(3)=1-2=-1 n=107:Floor[107/2]=53,Phi[107]=2.53, P[106]=53, a(107)=53-53=0; if n is safe prime, then a(n)=0. n=128:Floor[128/2]=64,P[Phi[128]]=P[64]=2, a(128)=64-2=62.
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MATHEMATICA
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mf[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] Table[Floor[n/2//N]-mf[EulerPhi[n]], {w, 3, 128}]
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CROSSREFS
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Cf. A004526, A068211, A006530, A000010, A005385, A005384.
Sequence in context: A088002 A030109 A058208 this_sequence A127474 A078024 A112469
Adjacent sequences: A070814 A070815 A070816 this_sequence A070818 A070819 A070820
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KEYWORD
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easy,sign
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 10 2002
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