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
8 = phi(15) = phi(16) = phi(20) = phi(24) = phi(30).
MATHEMATICA
a = Table[ 0, {5000} ]; Do[ p = EulerPhi[ n ]; If[ p < 5001, a[[ p ]]++ ], {n, 1, 15000} ]; Select[ Range[ 5000 ], a[[ # ]] == 5 & ]
PROG
(PARI) is(n)=sum(k=1, n, eulerphi(k)==n)==5 \\ Charles R Greathouse IV, Mar 03 2014
(PARI) is(k) = invphiNum(k) == 5 \\ Amiram Eldar, Nov 17 2024, using Max Alekseyev's invphi.gp
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Robert G. Wilson v, Apr 18 2001
STATUS
approved