OFFSET
1,1
COMMENTS
Apart from 5, all terms are in A045762, numbers such that 2^n-1 is not prime. - Michel Marcus, Nov 12 2014
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
For n=5, 2^5-1=31 is divisible by 6*5+1=31.
MATHEMATICA
Select[Range[800], PowerMod[2, #, 6#+1]==1&] (* Harvey P. Dale, Oct 24 2017 *)
PROG
(PARI) select( {is_A038844(n)=Mod(2, n*6+1)^n==1}, [1..999]) \\ M. F. Hasler, Aug 17 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Michel Marcus, Nov 12 2014
STATUS
approved