OFFSET
1,1
COMMENTS
The sequence contains all terms up to 10^10. There are no terms as yet for which (p^12 + 5)/6 is also prime.
No terms < 10^11 with (p^12 + 5)/6 prime. - Chai Wah Wu, Jan 27 2015
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..67
PROG
(Python)
from gmpy2 import is_prime, t_divmod
A253941_list = []
for p in range(1, 10**6, 2):
....if is_prime(p):
........p2, x = p**2, 1
........for i in range(5):
............x *= p2
............q, r = t_divmod(x+5, 6)
............if r or not is_prime(q):
................break
........else:
............A253941_list.append(p) # Chai Wah Wu, Jan 22 2015
(PARI) lista(nn) = forprime(p=5, nn, if(ispseudoprime((p^2 + 5)/6) && ispseudoprime((p^4 + 5)/6) && ispseudoprime((p^6 + 5)/6) && ispseudoprime((p^8 + 5)/6) && ispseudoprime((p^10 + 5)/6), print1(p, ", "))); \\ Jinyuan Wang, Mar 01 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jan 20 2015
EXTENSIONS
a(15)-a(26) from Chai Wah Wu, Jan 22 2015
STATUS
approved