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A230120
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a(n) is the number of evil integers (A001969) not exceeding n and respectively prime to n.
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2
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0, 0, 0, 1, 1, 1, 3, 2, 1, 2, 5, 1, 6, 3, 0, 4, 7, 2, 9, 3, 4, 5, 10, 3, 8, 6, 5, 7, 13, 3, 15, 8, 6, 8, 12, 4, 18, 9, 7, 8, 20, 4, 20, 10, 5, 11, 23, 5, 24, 9, 8, 12, 25, 6, 19, 14, 11, 14, 29, 5, 30, 15, 12, 16, 22, 7, 33, 15, 12, 12, 34, 8, 36, 18, 10, 18
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OFFSET
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1,7
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COMMENTS
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See comment in A230070, taking into account the equality a(n) = phi(n) -
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LINKS
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FORMULA
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For odd evil prime p (A027699), a(p) = (p-3)/2; for odd odious prime p (A027697), a(p) = (p-1)/2.
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MATHEMATICA
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evils=Select[Range[rng=100], EvenQ[DigitCount[#, 2][[1]]]&]; tmp=0; Table[Count[Map[CoprimeQ[n, #]&, Take[evils, tmp=NestWhile[#+1&, tmp+1, evils[[#]]<n && !(Length[evils]<=tmp+1)&]-1]], True], {n, rng}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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