A098216 Nonprime numbers n for which cototient[n]=n-phi[n] is a decimal repdigit.

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

Offset

1,2

Links

Table of n, a(n) for n=1..55.

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

Cf. A096503, A010785.

Sequence in context: A050655 A117098 A077136 * A341321 A063806 A323521

Adjacent sequences: A098213 A098214 A098215 * A098217 A098218 A098219

Keyword

nonn,base

Author

Labos Elemer, Oct 22 2004

Status

approved