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A271396
Integers k such that 3*k!!! - 1 is prime where k!!! is A007661(k).
1
0, 1, 2, 4, 5, 6, 7, 8, 10, 17, 25, 28, 31, 37, 38, 39, 46, 47, 49, 55, 67, 82, 85, 94, 98, 115, 120, 129, 167, 214, 216, 267, 293, 580, 732, 857, 993, 1012, 1069, 1308, 1430, 2366, 2974, 4017, 4870, 9034, 9061, 9752, 10657, 13847, 25390
OFFSET
1,3
COMMENTS
Corresponding primes are 2, 2, 5, 11, 29, 53, 83, 239, 839, 628319, 1825823999, 51123071999, ...
EXAMPLE
4 is a term because 3*4!!! - 1 = 11 is prime.
PROG
(PARI) is(k) = ispseudoprime(3*prod(i=0, (k-2)\3, k-3*i) - 1); \\ Jinyuan Wang, Jun 09 2021
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Apr 06 2016
EXTENSIONS
a(46)-a(50) from Jinyuan Wang, Jun 09 2021
a(51) from Michael S. Branicky, Aug 09 2024
STATUS
approved