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A060675 Numbers n such that phi(x) = n has exactly 12 solutions. 1
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 (list; graph; refs; listen; history; text; internal format)
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 A127338

Adjacent sequences:  A060672 A060673 A060674 * A060676 A060677 A060678

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 18 2001

STATUS

approved

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Last modified August 12 15:13 EDT 2022. Contains 356077 sequences. (Running on oeis4.)