OFFSET
1,2
COMMENTS
A number n is a k-Lehmer number if there exist a k such that phi(n) divides (n-1)^k.
The values of a(10) and a(11) computed by N. McNew in the linked paper are smaller than mine. I provide a link to my full list so that it could be independently checked.
LINKS
José María Grau and Antonio M. Oller-Marcén, On k-Lehmer numbers, Integers, 12(2012), #A37.
Nathan McNew, Radically weakening the Lehmer and Carmichael conditions International Journal of Number Theory 9 (2013), 1215-1224.
Giovanni Resta, k-Lehmer numbers composite k-Lehmer numbers up to 10^12.
EXAMPLE
There are 4 k-Lehmer numbers up to 10^2, namely 15, 51, 85, and 91, so a(2) = 4.
MATHEMATICA
kLQ[n_] := n > 1 && ! PrimeQ[n] && Mod[n-1, Times @@ First /@ FactorInteger@ EulerPhi@n] == 0; Table[Length@ Select[Range[2, 10^k], kLQ], {k, 6}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Jan 01 2014
STATUS
approved