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A098217 Cototients of terms from A098216. By definitions these cototient values are decimal repdigits. 1
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; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
It is believed that for every repdigit r>1, inverse[cototient[r]] has solution, usually more than one.
LINKS
MATHEMATICA
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]
CROSSREFS
Sequence in context: A079533 A072872 A135359 * A151846 A131118 A140765
KEYWORD
nonn,base
AUTHOR
Labos Elemer, Oct 22 2004
STATUS
approved

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Last modified March 1 11:54 EST 2024. Contains 370432 sequences. (Running on oeis4.)