A060674 Numbers k such that phi(x) = k has exactly 11 solutions.

48, 512, 540, 1000, 1836, 2136, 2176, 2320, 2340, 3216, 3648, 3936, 4284, 4352, 4356, 4784, 5088, 5640, 5936, 6216, 6576, 6816, 7120, 7224, 7280, 7752, 8100, 8184, 8496, 8520, 8760, 9040, 9296, 9660, 9680, 9900, 9996, 10332, 10860, 11640, 11680, 11844

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Example

48 = phi(65) = phi(104) = phi(105) = phi(112) = phi(130) = phi(140) = phi(144) = phi(156) = phi(168) = phi(180) = phi(210).

Mathematica

a = Table[ 0, {12500} ]; Do[ p = EulerPhi[ n ]; If[ p < 12501, a[ [ p ] ]++ ], {n, 1, 50000} ]; Select[ Range[ 12500 ], a[ [ # ] ] == 11 & ]

Prog

(PARI) is(n)=sum(i=1, n, eulerphi(i)==n)==11 \\ Charles R Greathouse IV, Mar 03 2014
(PARI) is(k) = invphiNum(k) == 11 \\ Amiram Eldar, Nov 17 2024, using Max Alekseyev's invphi.gp

Crossrefs

Cf. A000010.

Number of solutions: A007617 (0), A007366 (2), A007367 (3), A060667 (4), A060668 (5), A060669 (6), A060670 (7), A060671 (8), A060672 (9), A060673 (10), this sequence (11), A060675 (12).

Sequence in context: A198398 A211149 A034778 * A233165 A247743 A189346

Adjacent sequences: A060671 A060672 A060673 * A060675 A060676 A060677

Keyword

nonn,changed

Author

Robert G. Wilson v, Apr 18 2001

Status

approved