OFFSET
1,1
COMMENTS
Contains the Carmichael numbers (A002997).
Conjecture: the relative asymptotic density of the Carmichael numbers in this sequence exists, is positive and smaller than 1.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
J. M. Grau and Antonio Oller-Marcén, Generalizing Giuga's conjecture, arXiv:1103.3483 [math.NT], 2011.
MATHEMATICA
Select [1 + Range[100000], ! PrimeQ[#] && IntegerQ[2 (# -1)/ CarmichaelLambda[#]] &]
PROG
(PARI) is(n)=!isprime(n) && (2*n-2)%lcm(znstar(n)[2])==0 && n>1 \\ Charles R Greathouse IV, Nov 13 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Nov 11 2013
STATUS
approved