OFFSET
1,2
COMMENTS
Novák numbers n that are 2n Novák-Carmichael. See Kalmynin link.
LINKS
Alexander Kalmynin, On Novák numbers, arXiv:1611.00417 [math.NT], 2016. See Theorem 7 p. 11.
MATHEMATICA
Reap[Do[If[PowerMod[2, n, n]+1 == n && Divisible[2n, CarmichaelLambda[2n]], Print[n]; Sow[n]], {n, 2 10^6}]][[2, 1]] (* Jean-François Alcover, Sep 25 2018 *)
PROG
(PARI) isnov(n) = Mod(2, n)^n==-1; \\ A006521
isnovcar(n) = n%lcm(znstar(n)[2])==0; \\ A124240
isok(n) = isnov(n) && isnovcar(2*n);
(Python)
from itertools import count, islice
from sympy.ntheory.factor_ import reduced_totient
def A289257gen(): return filter(lambda n:2*n % reduced_totient(2*n) == 0 and pow(2, n, n)==n-1, count(1))
A289257_list = list(islice(A289257gen(), 20)) # Chai Wah Wu, Dec 11 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Jun 29 2017
STATUS
approved