A060675 Numbers n such that phi(x) = n has exactly 12 solutions.

160, 168, 352, 448, 816, 928, 972, 1024, 1176, 1848, 2464, 3040, 3808, 4152, 4440, 4512, 4736, 4944, 5104, 5152, 5160, 5304, 5952, 6408, 6656, 6672, 6784, 7648, 8384, 8704, 8904, 10432, 10528, 10624, 11000, 11008, 11456, 11776, 12048, 12416, 13024, 13032

Offset

1,1

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Example

160 = phi(187) = phi(205) = phi(328) = phi(352) = phi(374) = phi(400) = phi(410) = phi(440) = phi(492) = phi(528) = phi(600) = phi(660).

Mathematica

a = Table[ 0, {15000} ]; Do[ p = EulerPhi[ n ]; If[ p < 15001, a[ [ p ] ]++ ], {n, 1, 60000} ]; Select[ Range[ 15000 ], a[ [ # ] ] == 12 & ]
Union[Transpose[Select[Tally[EulerPhi[Range[100000]]], #[[2]]==12&]][[1]]] (* Harvey P. Dale, Oct 05 2015 *)

Prog

(PARI) is(n)=sum(i=1, n, eulerphi(i)==n)==12 \\ Charles R Greathouse IV, Mar 03 2014

Crossrefs

Cf. A007366, A007367.

Sequence in context: A013455 A013465 A013466 * A171225 A290463 A367206

Adjacent sequences: A060672 A060673 A060674 * A060676 A060677 A060678

Keyword

nonn

Author

Robert G. Wilson v, Apr 18 2001

Status

approved