OFFSET
1,1
COMMENTS
All terms <= 10^9 are prime, are there any composite terms?
MATHEMATICA
Select[Range[5, 777*10^4, 12], PowerMod[2, #(2#-1)-1, #(2#-1)]==1&] (* Harvey P. Dale, Sep 07 2021 *)
PROG
(PARI)
{ forstep (n=5, 10^9, 12,
m = (2*n-1)*n;
t = Mod(2, m)^(m-1);
if ( component(t, 2) == 1,
print1(n, ", "); /* print term */
/* if ( !isprime(n), print1(n, ", ") ); */ /* print only nonprime terms */
); ); } /* Joerg Arndt, Apr 01 2011 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Alzhekeyev Ascar M, Mar 20 2011
STATUS
approved