%I #31 Apr 11 2023 03:47:30
%S 2,3,6,18,19,82,1298,3139,3687,4637
%N Numbers k such that k!^2 / 2 + 1 is prime.
%e 3!^2 / 2 + 1 = 6^2/2 + 1 = 19, a prime number, so 3 is a term.
%o (PARI) isok(k) = (k>1) && isprime(k!^2 / 2 + 1); \\ _Michel Marcus_, Jan 15 2023
%Y Cf. A002981, A046029, A358805, A358878.
%K nonn,hard,more
%O 1,1
%A _Arsen Vardanyan_, Dec 18 2022
%E a(7) from _Michael S. Branicky_, Dec 18 2022
%E a(8)-a(10) from _Michael S. Branicky_, Apr 10 2023