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A339878 Carmichael numbers k such that phi(k) divides p*(k - 1) for some prime factor p of k - 1. 4
1729, 3069196417, 23915494401, 1334063001601, 6767608320001, 33812972024833, 1584348087168001, 1602991137369601, 6166793784729601, 1531757211193440001 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The first ten terms are all in A339818, none is in A339869, and all except a(2) and a(6) are in A339909.
Also, for all ten, a(n) == 1 (mod 64). (Cf. a similar comment in A338998).
LINKS
Thomas Ordowski & Amiram Eldar, A new look at the Lehmer's totient problem, SeqFan, February 10 2019.
MATHEMATICA
carmichaels = Cases[Import["https://oeis.org/A002997/b002997.txt", "Table"], {_, _}][[;; , 2]]; q[n_] := Module[{p = FactorInteger[n - 1][[;; , 1]], phi = EulerPhi[n]}, AnyTrue[(n - 1)*p, Divisible[#, phi] &]]; Select[carmichaels, q] (* Amiram Eldar, Dec 26 2020 *)
CROSSREFS
Intersection of A002997 and A338998.
Cf. also A339818, A339869, A339909.
Sequence in context: A306657 A048949 A339909 * A258166 A130876 A234706
KEYWORD
nonn,more
AUTHOR
Antti Karttunen (after Thomas Ordowski's and Amiram Eldar's SeqFan-posting), Dec 26 2020
EXTENSIONS
a(10) from Amiram Eldar, Dec 26 2020
STATUS
approved

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Last modified March 28 16:34 EDT 2024. Contains 371254 sequences. (Running on oeis4.)