OFFSET
1,2
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..500
MAPLE
for n from 1 to 5000 do if 4^n mod n = 4 mod n and not isprime(n) then print(n) fi od; # Gary Detlefs, May 14 2012
MATHEMATICA
Select[Range[4800], ! PrimeQ[ # ] && Mod[4^#, # ] == Mod[4, # ] &]
Join[{1, 4}, Select[Range[5000], !PrimeQ[#]&&PowerMod[4, #, #]==4&]] (* Harvey P. Dale, Apr 09 2018 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Farideh Firoozbakht, Sep 12 2006
STATUS
approved