OFFSET
1,1
COMMENTS
Conjecture: A055553(n)/a(n) has a limit strictly smaller than 1 as n tends to infinity.
LINKS
J. M. Grau and A. Oller-Marcén, On the congruence sum_{j=1}^{n-1} j^{k(n-1)} == -1 (mod n). k-strong Giuga and k-Carmichael numbers, arXiv:1311.3522 [math.NT], 2013.
MATHEMATICA
For[k = 4; cnt = 0, True, k++, If[CompositeQ[k] && Divisible[2k-2, CarmichaelLambda[k]], cnt++]; If[IntegerQ[n = Log[10, k+1]], Print[n, " ", cnt]]]; (* Jean-François Alcover, Feb 16 2019 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
José María Grau Ribas, Mar 02 2014
EXTENSIONS
a(8)-a(10) from Giovanni Resta, Mar 03 2014
STATUS
approved