OFFSET
1,1
COMMENTS
All values of n are even (since there are no even Carmichael numbers). Small values happen to be congruent to 18 modulo 66. This first fails for a(34)=5206142, which yields the Carmichael number 86921811895459937817345 = (3*5*29*83777)*41649137*57267563. Below this, only 4 values of n (18, 216, 299790 and 446310) correspond to Carmichael numbers with at least 4 prime factors. Other values of n must be of the form 1848k+942, with k given by A101186.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
GĂ©rard P. Michon, Generic Carmichael Numbers.
EXAMPLE
a(1) = 18 corresponds to a 4-factor Carmichael number: 3664585 = 127 *(5*29) * 199.
MATHEMATICA
CarmichaelNbrQ[n_] := ! PrimeQ[n] && Mod[n, CarmichaelLambda[n]] == 1; Select[ Range[4000000], CarmichaelNbrQ[(7# + 1)(8# + 1)(11# + 1)] &] (* Robert G. Wilson v, Aug 24 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Gerard P. Michon, Dec 08 2004
STATUS
approved