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A374901
Numbers k such that k!^2 + ((k - 1)!^2) + 1 is prime.
1
1, 3, 4, 6, 10, 11, 118, 271, 288, 441, 457, 2931, 5527, 6984, 9998, 10395, 13703
OFFSET
1,2
COMMENTS
a(18) > 15000 - Karl-Heinz Hofmann, Aug 23 2024
EXAMPLE
4 is a term, because 4!^2 + 3!^2 + 1 = 576 + 36 + 1 = 613 is a prime number.
PROG
(PARI) is(k) = isprime((k!^2)+((k-1)!)^2+1);
(Python)
from itertools import count, islice
from sympy import isprime
def A374901_gen(): # generator of terms
f = 1
for k in count(1):
if isprime((k**2+1)*f+1):
yield k
f *= k**2
A374901_list = list(islice(A374901_gen(), 10)) # Chai Wah Wu, Oct 02 2024
KEYWORD
nonn,more
AUTHOR
Arsen Vardanyan, Jul 31 2024
EXTENSIONS
a(12)-a(14) from Michael S. Branicky, Aug 01 2024
a(15)-a(17) from Karl-Heinz Hofmann, Aug 23 2024
STATUS
approved