OFFSET
1,1
COMMENTS
If p-1 is squarefree, 2a(n) is the multiplicative order of 2 modulo every divisor d>1 of (2^p+1)/3. - Vladimir Shevelev, Jul 15 2008
MATHEMATICA
a = {}; Do[c = (2^Prime[x] + 1)/3; If[PrimeQ[c] == False, AppendTo[a, Prime[x]]], {x, 2, 100}]; a
Select[Prime[Range[2, 100]], CompositeQ[(2^#+1)/3]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 07 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Feb 09 2007
STATUS
approved