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Numbers k such that k! + (k!/2) - 1 is prime.
4

%I #24 Apr 02 2023 10:27:36

%S 2,5,7,15,20,47,84,138,169,257,263,431,559,2939,4403,4870,5273

%N Numbers k such that k! + (k!/2) - 1 is prime.

%C Numbers k such that A070960(k) - 1 is prime.

%C No more terms < 10000. - _Vaclav Kotesovec_, Dec 12 2022

%o (PARI) is(k) = isprime(k!+(k!/2)-1);

%Y Cf. A070960, A358805.

%K nonn,more

%O 1,1

%A _Arsen Vardanyan_, Dec 04 2022

%E a(14)-a(17) from _Vaclav Kotesovec_, Dec 07 2022