OFFSET
1,1
COMMENTS
a(15) > 1099997, if it exists. - Karl-Heinz Hofmann, Jul 27 2021
These are primes p such that 2^((2^p-2)/p) == 1 (mod (2^p-2)/p+1) if and only if there are no pseudoprimes of the form (2^q-2)/q+1 with q prime. - Thomas Ordowski, Aug 29 2021
EXAMPLE
7 is a term because (2^7 - 2)/7 + 1 = 19 is prime.
MATHEMATICA
Select[Prime@ Range[10^3], PrimeQ[(2^# - 2)/# + 1] &] (* Michael De Vlieger, Oct 12 2021 *)
PROG
(PARI) lista(lim)={forprime(p=1, lim, if(ispseudoprime((2^p-2)/p+1), print1(p, ", ")))}
(PARI) c3(p) = {s=3; for(x=1, p, s=(s^2)%((2^p-2)/p+1)); if(s==9, print1(p, ", "))} /* PRP Test */
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jorge Coveiro, May 15 2021
EXTENSIONS
a(14) from Karl-Heinz Hofmann, Jun 11 2021
STATUS
approved