OFFSET
1
COMMENTS
This is the Legendre-Jacobi-Kronecker symbol (2/p) where p is the n-th prime.
Appears to be the constant term of the minimal polynomial of cos(Pi/prime(n)). - Ethan Beihl, Oct 27 2016
For n > 1 a(n) is the +-1 value of prime(n) as a near-Wieferich prime, i.e., a(n) is positive or negative depending on whether 2^((p-1)/2) == +1 + A*p (mod p^2) or 2^((p-1)/2) == -1 + A*p (mod p^2) (cf. JeppeSN link). - Felix Fröhlich, Jul 01 2022
LINKS
Felix Fröhlich, Table of n, a(n) for n = 1..10000
JeppeSN, Check a WW find with PARI/GP, PrimeGrid forum (Message 145728).
PROG
(PARI) a(n) = kronecker(2, prime(n)) \\ Felix Fröhlich, Jul 01 2022
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Jun 22 2013
STATUS
approved