login
Numbers k such that 5*k! + 1 is prime.
7

%I #15 Jul 04 2024 01:40:11

%S 2,3,5,10,11,12,17,34,74,136,155,259,271,290,352,479,494,677,776,862,

%T 921,932,2211,3927,4688,12567

%N Numbers k such that 5*k! + 1 is prime.

%C a(26) > 4700. - _Jinyuan Wang_, Feb 04 2020

%e k = 3 is here because 5*3! + 1 = 31 is prime.

%o (PARI) is(k) = ispseudoprime(5*k!+1); \\ _Jinyuan Wang_, Feb 04 2020

%Y Cf. A002981, A051915, A076679, A076680, A076682, A076683, A178488, A180626, A126896.

%K nonn,more

%O 1,1

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

%E a(25) from _Jinyuan Wang_, Feb 04 2020

%E a(26) from _Michael S. Branicky_, Jul 03 2024