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A098216 Nonprime numbers n for which cototient[n]=n-phi[n] is a decimal repdigit. 3
1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 21, 25, 27, 30, 35, 49, 60, 86, 90, 93, 120, 121, 145, 159, 172, 175, 195, 231, 245, 253, 279, 291, 327, 365, 497, 535, 559, 693, 703, 737, 886, 979, 981, 993, 1037, 1111, 1121, 1411, 1457, 1517, 1617, 1772, 1774, 2047, 2059 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
n=97002, n-phi[n]=66666
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: A050655 A117098 A077136 * A341321 A063806 A323521
KEYWORD
nonn,base
AUTHOR
Labos Elemer, Oct 22 2004
STATUS
approved

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Last modified June 12 13:39 EDT 2024. Contains 373331 sequences. (Running on oeis4.)