OFFSET
1,2
COMMENTS
a(n) = 0 where n=183 (p=1093) and n=490 (p=3511).
From Felix Fröhlich, Sep 13 2019: (Start)
Conjecture: a(n) is the residue A036968(p-1) (mod p) for p = prime(n).
If the above conjecture is true, then a(n) = 0 if and only if p is a Wieferich prime (A001220) (cf. Hu et al., 2019, section 1.3). (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Su Hu, Min-Soo Kim, Pieter Moree and Min Sha, Irregular primes with respect to Genocchi numbers and Artin's primitive root conjecture, arXiv:1809.08431 [math.NT], 2019; Journal of Number Theory 205 (2019), 59-80, DOI:10.1016/j.jnt.2019.03.012.
MAPLE
f:= p -> (2&^p-2 mod p^2)/p:
seq(f(ithprime(i)), i=1..100); # Robert Israel, Nov 03 2024
MATHEMATICA
aa = {}; Do[AppendTo[aa, Mod[(2^Prime[n] - 2)/Prime[n], Prime[n]]], {n, 1, 100}]; aa
PROG
(PARI) a(n) = my(p=prime(n)); lift(Mod(((2^p-2)/p), p)) \\ Felix Fröhlich, Sep 13 2019
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Artur Jasinski, Jun 28 2010
STATUS
approved