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Search: id:A098217
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| A098217 |
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Cototients of terms from A098216. By definitions these cototient vakues are decimal repdigits. |
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+0
2
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| 0, 2, 4, 4, 3, 6, 8, 8, 7, 8, 9, 5, 9, 22, 11, 7, 44, 44, 66, 33, 88, 11, 33, 55, 88, 55, 99, 111, 77, 33, 99, 99, 111, 77, 77, 111, 55, 333, 55, 77, 444, 99, 333, 333, 77, 111, 77, 99, 77, 77, 777, 888, 888, 111, 99, 999, 777, 111, 99, 99, 555, 111, 999, 999, 999, 111, 1111
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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It is believed that for every repdigit r>1, inverse[cototient[r]] has solution, usually more than one.
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MATHEMATICA
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ta={{0}}; Do[s=Length[Union[IntegerDigits[n-EulerPhi[n]]]]; If[Equal[s, 1]&&!PrimeQ[n], Print[{n, n-EulerPhi[n]}]; ta=Append[ta, n]], {n, 1, 100000}]; ta=Delete[ta, 1]; ta-EulerPhi[ta]
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CROSSREFS
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Cf. A096503, A010785.
Sequence in context: A079533 A135359 A072872 this_sequence A151846 A131118 A140765
Adjacent sequences: A098214 A098215 A098216 this_sequence A098218 A098219 A098220
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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), Oct 22 2004
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