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Search: id:A072022
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| A072022 |
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Smallest x so that the number of nonprimes (i.e. 1 and composites) in the reduced residue set (RSS(n)) of n equals n. |
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4
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| 1, 5, 7, 15, 26, 11, 13, 38, 102, 17, 19, 25, 0, 23, 35, 144, 74, 198, 29, 31, 75, 57, 104, 94, 37, 55, 69, 41, 43, 118, 0, 47, 81, 128, 87, 134, 53, 93, 480, 146, 77, 59, 61, 117, 111, 166, 172, 67, 250, 91, 71, 73, 350, 194, 129, 202, 79, 206, 212, 83, 214, 153, 218
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=Min{x; A048864(x)=n}; a(n)=0 if no such number exists.
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EXAMPLE
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n = 15: RRS[15] = {1,2,4,7,8,11,13,14} of which nonprimes = cRRS[15] = {1,4,8,14}, i.e. 4 terms; since 15 is smallest such number, so a(4) = 15. a(m) = 0 for m = {13,31,70,119,189,210,235,236}
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MATHEMATICA
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f[x_] := EulerPhi[x]-PrimePi[x]+Length[FactorInteger[x]] t=Table[0, {256}]; Do[s=f[n]; If[s<257&&t[[s]]==0, t[[s]]=n], {n, 3, 1000000}]; t
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CROSSREFS
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Cf. A048864, A072023.
Sequence in context: A068580 A110994 A015833 this_sequence A003429 A076860 A067589
Adjacent sequences: A072019 A072020 A072021 this_sequence A072023 A072024 A072025
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jun 06 2002
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