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Numbers k such that 9*k! - 1 is prime.
8

%I #16 Nov 03 2024 02:13:25

%S 2,3,12,15,16,25,30,38,59,82,114,168,172,175,213,229,251,302,311,554,

%T 2538,3050,3363,12316

%N Numbers k such that 9*k! - 1 is prime.

%C a(22) > 2575. - _Jinyuan Wang_, Feb 03 2020

%H <a href="/index/Pri#primepop">Index entries for sequences related to numbers of primes of the form k*n!+-1</a>

%t fQ[n_] := PrimeQ[9 n! - 1]; k = 0; lst = {}; While[k < 1501, If[ fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst

%o (PARI) is(k) = ispseudoprime(9*k!-1); \\ _Jinyuan Wang_, Feb 03 2020

%Y Cf. A002982, A076133, A076134, A099350, A099351, A180627, A180628, A180629, A180631.

%K nonn,more

%O 1,1

%A _Robert G. Wilson v_, Sep 13 2010

%E a(21) from _Jinyuan Wang_, Feb 03 2020

%E a(22)-a(23) from _Michael S. Branicky_, Apr 25 2023

%E a(24) from _Michael S. Branicky_, Nov 02 2024