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Search: id:A073758
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| A073758 |
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Smallest number of "unrelated set" belonging to n [=URS(n)]. Least number, neither divisor nor relatively prime to n. Or a(n)=0 if unrelated set is empty. |
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+0
5
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| 0, 0, 0, 0, 0, 4, 0, 6, 6, 4, 0, 8, 0, 4, 6, 6, 0, 4, 0, 6, 6, 4, 0, 9, 10, 4, 6, 6, 0, 4, 0, 6, 6, 4, 10, 8, 0, 4, 6, 6, 0, 4, 0, 6, 6, 4, 0, 9, 14, 4, 6, 6, 0, 4, 10, 6, 6, 4, 0, 8, 0, 4, 6, 6, 10, 4, 0, 6, 6, 4, 0, 10, 0, 4, 6, 6, 14, 4, 0, 6, 6, 4, 0, 8, 10, 4, 6, 6, 0, 4, 14, 6, 6, 4, 10, 9, 0, 4, 6
(list; graph; listen)
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OFFSET
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1,6
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EXAMPLE
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n=20: unrelated set to 20 ={6,8,12,14,15,16,18},smallest is a(20)=6.
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MATHEMATICA
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tn[x_] := Table[w, {w, 1, x}]; di[x_] := Divisors[x]; dr[x_] := Union[di[x], rrs[x]]; rrs[x_] := Flatten[Position[GCD[tn[x], x], 1]]; unr[x_] := Complement[tn[x], dr[x]]; Table[Min[unr[w]], {w, 1, 128}]. (+ or -Infinity is replaced by 0)
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CROSSREFS
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Cf. A045763.
Sequence in context: A021715 A075443 A021250 this_sequence A133995 A019629 A073759
Adjacent sequences: A073755 A073756 A073757 this_sequence A073759 A073760 A073761
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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), Aug 08 2002
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