

A339878


Carmichael numbers k such that phi(k) divides p*(k  1) for some prime factor p of k  1.


4




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

Table of n, a(n) for n=1..10.
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
Adjacent sequences: A339875 A339876 A339877 * A339879 A339880 A339881


KEYWORD

nonn,more


AUTHOR

Antti Karttunen (after Thomas Ordowski's and Amiram Eldar's SeqFanposting), Dec 26 2020


EXTENSIONS

a(10) from Amiram Eldar, Dec 26 2020


STATUS

approved



