|
%I #11 Mar 07 2021 09:24:58
%S 3,7,8,15,19,29,36,43,51,158,160,203,432,909,1235,3209
%N Numbers k such that 7*k! + 1 is prime.
%C a(17) > 5830. - _Jinyuan Wang_, Feb 05 2020
%e k = 3 is here because 7*3! + 1 = 43 is prime.
%o (PARI) is(k) = ispseudoprime(7*k!+1); \\ _Jinyuan Wang_, Feb 05 2020
%o (Python)
%o from sympy import isprime
%o from math import factorial
%o def aupto(m): return [k for k in range(m+1) if isprime(7*factorial(k)+1)]
%o print(aupto(300)) # _Michael S. Branicky_, Mar 07 2021
%Y Cf. A002981, A051915, A076679, A076680, A076681, A076682, A178488, A180626, A126896.
%K nonn,more
%O 1,1
%A Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002
|
