|
|
A226523
|
|
a(n) = 0 if p=2, 1 if 2 is a square mod p, -1 otherwise, where p = prime(n).
|
|
6
|
|
|
0, -1, -1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, -1, -1, -1, 1, 1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, -1, 1, -1, -1, -1, 1, 1, -1, 1, -1, 1, -1, -1, 1, 1, 1, -1, 1, 1, -1, 1, -1, 1, -1, -1, -1, 1, 1, -1, -1, 1, -1, -1, 1, 1, 1, -1, -1, 1, -1, -1, 1, 1, -1, -1, 1, 1, 1, -1, 1, 1, -1
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
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
|
|
|
PROG
|
|
|
CROSSREFS
|
A038871 lists the primes for which a(n)=1, A003629 those for which a(n)=-1.
|
|
KEYWORD
|
sign
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|