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A370664
Numbers k such that A176972(k) = 7^k + 7*k + 1 is prime.
1
0, 5, 11, 1389, 5351, 6207, 31173
OFFSET
1,2
COMMENTS
If it exists, a(8) > 50000.
PROG
(PARI) is(n) = ispseudoprime(7^n+7*n+1)
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Hugo Pfoertner, Feb 26 2024
STATUS
approved