This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A242487 #63 May 04 2025 01:58:53
%S A242487 0,3,8,13,19,423,585,2746,2855
%N A242487 Numbers k such that (2*k)! + k! + 1 is prime.
%C A242487 a(10) > 10000. - _Michael S. Branicky_, May 03 2025
%e A242487 0! + 0! + 1 = 3 is prime.
%e A242487 6! + 3! + 1 = 727 is prime.
%p A242487 select(k->isprime(factorial(2*k)+factorial(k)+1),[$0..600]); # _Muniru A Asiru_, May 27 2018
%t A242487 Flatten[{0, Select[Range[100], PrimeQ[(2*#)! + #! + 1] &]}] (* _Vaclav Kotesovec_, Mar 25 2018 *)
%o A242487 (PARI) isok(k) = ispseudoprime((2*k)!+k!+1); \\ _Altug Alkan_, Mar 22 2018
%Y A242487 A300947 gives the primes.
%Y A242487 Cf. A002981, A237443.
%K A242487 nonn,more
%O A242487 1,2
%A A242487 _Seiichi Manyama_, Mar 22 2018
%E A242487 a(8)-a(9) from _Michael S. Branicky_, Apr 16 2023