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 A344991 #48 Jun 26 2021 16:58:39
%S A344991 1,3,5,15,20,44,45,73,80,93,295,5395
%N A344991 Numbers k such that (2*k+1)*k!-1 is prime.
%C A344991 a(13) > 10^4.
%p A344991 select(k -> isprime((2*k+1)*k!-1), [$1 .. 300])[];
%t A344991 Do[If[PrimeQ[(2*k + 1)*Factorial[k] - 1], Print[k]], {k, 1, 3000}]
%o A344991 (PARI) for(k=1, 3000, if(isprime((2*k+1)*k!-1), print1(k", ")))
%o A344991 (SageMath)
%o A344991 for k in range(1, 3000):
%o A344991 if is_prime((2*k+1)*factorial(k) - 1):
%o A344991 print(k)
%Y A344991 Cf. A002982, A344963.
%K A344991 nonn,hard,more
%O A344991 1,2
%A A344991 _Reza K Ghazi_, Jun 07 2021