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A069946 Numbers k such that phi(k) mod core(k) = 1 where core(k) is the squarefree part of k. 1
2, 12, 48, 60, 63, 75, 175, 192, 363, 405, 468, 704, 768, 816, 867, 891, 960, 980, 1008, 1020, 1587, 1875, 2023, 2107, 2331, 2475, 2523, 2527, 2800, 2835, 3072, 3075, 3185, 3332, 3757, 4100, 4335, 4477, 4851, 5043, 5780, 6171, 6292, 6627, 6727, 6877, 7220 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
This sequence is infinite. For example, 3*4^k is a term for all k > 0, since core(3*4^k) = 3, phi(3*4^k) = 4^k and 4^k == 1 (mod 3). - Amiram Eldar, Sep 03 2020
LINKS
MATHEMATICA
core[n_] := Times @@ (First[#]^Mod[Last[#], 2] & /@ FactorInteger[n]); Select[Range[10^4], Mod[EulerPhi[#], core[#]] == 1 &] (* Amiram Eldar, Sep 03 2020 *)
PROG
(PARI) for(n=1, 15000, if(eulerphi(n)%core(n)==1, print1(n, ", ")))
CROSSREFS
Sequence in context: A302447 A319763 A320684 * A176684 A216152 A048501
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 27 2002
EXTENSIONS
Name corrected by Amiram Eldar, Sep 05 2020
STATUS
approved

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Last modified May 27 01:42 EDT 2024. Contains 372847 sequences. (Running on oeis4.)