OFFSET
1,1
COMMENTS
Inspired by the question: is n == 1 mod phi(n) for n composite?
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(1) = 2 since the first two numbers k such that 3 | phi(k) are 7 and 9, and 9 - 7 = 2.
MATHEMATICA
Differences @ Position[EulerPhi[Range[200]], _?(Divisible[#, 3] &)] // Flatten (* Amiram Eldar, Feb 29 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
J. Perry (johnandruth(AT)jrperry.orangehome.co.uk), Sep 06 2008
EXTENSIONS
Offset corrected and more terms added by Amiram Eldar, Feb 29 2020
STATUS
approved