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Numbers k such that 6*k! + 1 is prime.
7

%I #13 Jul 04 2024 20:06:21

%S 0,1,2,3,7,8,9,12,13,18,24,38,48,60,113,196,210,391,681,739,778,1653,

%T 1778,1796,1820,2391,2505,4595,8937

%N Numbers k such that 6*k! + 1 is prime.

%C a(29) > 5800. - _Jinyuan Wang_, Feb 05 2020

%C a(30) > 12000. - _Michael S. Branicky_, Jul 04 2024

%e k = 3 is here because 6*3! + 1 = 37 is prime.

%o (PARI) is(k) = ispseudoprime(6*k!+1); \\ _Jinyuan Wang_, Feb 05 2020

%Y Cf. A002981, A051915, A076679, A076680, A076681, A076683, A178488, A180626, A126896.

%K nonn,more

%O 1,3

%A Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002

%E a(26) inserted by and a(29) from _Michael S. Branicky_, Jul 03 2024