A096503 Euler-phi of these numbers is a decimal repdigit.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 23, 24, 30, 46, 67, 69, 89, 92, 115, 134, 138, 178, 184, 223, 230, 276, 446, 669, 892, 1043, 1115, 1338, 1341, 1784, 2086, 2230, 2676, 2682, 446669, 666667, 893338, 895043, 902423, 1333334, 1340007, 1786676

Offset

1,2

Links

T. D. Noe, Table of n, a(n) for n = 1..182

D. Bressoud, CNT.m Computational Number Theory Mathematica package.

Example

n=88888892, A000010(n)=44444444.
Regular solutions: if x=repdigit+1 is prime, then phi[x]=repdigit (see A028988).

Mathematica

Needs["CNT`"]; t = {PhiInverse[1]}; Do[n = FromDigits[Table[i, {j}]]; AppendTo[t, PhiInverse[n]], {j, 18}, {i, 2, 8, 2}]; t2 = Union[Flatten[t]]; t (* T. D. Noe, Feb 25 2014 *)
Select[Range[2*10^5], Length@ Union@ IntegerDigits@ EulerPhi@ # == 1 &] (* Michael De Vlieger, Jul 02 2016 *)

Prog

(PARI) isok(n) = d = digits(eulerphi(n)); vecmin(d) == vecmax(d); \\ Michel Marcus, Feb 25 2014

Crossrefs

Cf. A010785, A028988.

Sequence in context: A243356 A347933 A117296 * A055238 A100952 A303332

Adjacent sequences: A096500 A096501 A096502 * A096504 A096505 A096506

Keyword

base,nonn

Author

Labos Elemer, Jul 12 2004

Status

approved