OFFSET
1,1
COMMENTS
Carmichael numbers k such that A034380(k) divides k-1.
A proper subset of Carmichael numbers in A173703.
The number of terms below 10^k for k=1,2,...,18 is 0, 0, 1, 5, 10, 15, 25, 56, 101, 184, 310, 508, 814, 1265, 1964, 2990, 4486, 6704. Cf. A055553.
Composite numbers k such that lcm(lambda(k),phi(k)/lambda(k)) divides k-1.
Problem: are there infinitely many such numbers?
LINKS
MATHEMATICA
Select[Range[3, 100000, 2], !PrimeQ[#] && Divisible[#-1, c = CarmichaelLambda[#]] && Divisible[c*(#-1), EulerPhi[#]] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar and Thomas Ordowski, Feb 08 2019
STATUS
approved