OFFSET
1,1
COMMENTS
Odd composite numbers k such that 5^((k-1)/2) == (5/k) = 1 (mod k), where (5/k) is the Jacobi symbol (or Kronecker symbol).
LINKS
Jianing Song, Table of n, a(n) for n = 1..1000
EXAMPLE
29539 is a term because 29539 = 109*271 is composite, 29539 == 9 (mod 10), and 5^((29539-1)/2) == 1 (mod 29539).
PROG
(PARI) isA375915(k) = (k>1) && !isprime(k) && (k%10==1 || k%10==9) && Mod(5, k)^((k-1)/2) == 1
CROSSREFS
| b=2 | b=3 | b=5 |
-----------------------------------+-------------------+---------+----------+
-----------------------------------+-------------------+---------+----------+
-----------------------------------+-------------------+---------+----------+
(b/k)=-1, b^((k-1)/2)==1 (mod k) | | | |
-----------------------------------+-------------------+---------+----------+
(union of first two) | | | |
-----------------------------------+-------------------+---------+----------+
(union of all three) | | | |
KEYWORD
nonn
AUTHOR
Jianing Song, Sep 02 2024
STATUS
approved