OFFSET
2,3
COMMENTS
For n > 2, the Mersenne number 2^n - 1 is a prime if and only if a(n) = 0. See comments in A003010.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 2..3322
FORMULA
a(prime(n)) = A095847(n).
PROG
(PARI) a(n) = {my(pow = 2^n-1, res = Mod(4, pow)); for(i = 1, n-2, res = res^2 - 2); lift(res)}
first(n) = vector(n, i, a(i+1)) \\ David A. Corneth, Aug 12 2018
(Python)
def A317977(n):
m = 2**n-1
c = 4 % m
for _ in range(n-2):
c = (c**2-2) % m
return c # Chai Wah Wu, Oct 08 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas Ordowski, Aug 12 2018
EXTENSIONS
More terms from Michel Marcus and David A. Corneth, Aug 12 2018
STATUS
approved