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 A261730 #16 Sep 08 2022 08:46:13 %S A261730 1,2,8,85,308 %N A261730 Values of n such that prime(n)! - n! + 1 is a prime number. %C A261730 Inspired by A261457. %C A261730 Initial primes of the form prime(n)! - n! + 1 are 2, 5, 121645100408791681. %e A261730 For n=1, prime(1)!-1!+1 = 2 is a prime number. %t A261730 Select[Range[400], PrimeQ[Prime[#]! - #! + 1] &] (* _Vincenzo Librandi_, Aug 31 2015 *) %o A261730 (PARI) for(n=1, 1e3, if(isprime(prime(n)!-n!+1), print1(n", "))) %o A261730 (Magma) [n: n in [1..80] | IsPrime(Factorial(NthPrime(n))-Factorial(n)+1)]; // _Vincenzo Librandi_, Aug 31 2015 %Y A261730 Cf. A261457. %K A261730 nonn,more %O A261730 1,2 %A A261730 _Altug Alkan_, Aug 30 2015 %E A261730 a(4)-a(5) from _Giovanni Resta_, Aug 30 2015