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A096503
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Euler-phi of these numbers is a decimal repdigit.
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17
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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
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OFFSET
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1,2
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LINKS
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D. Bressoud, CNT.m Computational Number Theory Mathematica package.
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EXAMPLE
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Regular solutions: if x=repdigit+1 is prime, then phi[x]=repdigit (see A028988).
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MATHEMATICA
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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 *)
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PROG
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(PARI) isok(n) = d = digits(eulerphi(n)); vecmin(d) == vecmax(d); \\ Michel Marcus, Feb 25 2014
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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