A261730 Values of n such that prime(n)! - n! + 1 is a prime number.

1, 2, 8, 85, 308

Offset

1,2

Comments

Inspired by A261457.

Initial primes of the form prime(n)! - n! + 1 are 2, 5, 121645100408791681.

Links

Table of n, a(n) for n=1..5.

Example

For n=1, prime(1)!-1!+1 = 2 is a prime number.

Mathematica

Select[Range[400], PrimeQ[Prime[#]! - #! + 1] &] (* Vincenzo Librandi, Aug 31 2015 *)

Prog

(PARI) for(n=1, 1e3, if(isprime(prime(n)!-n!+1), print1(n", ")))
(Magma) [n: n in [1..80] | IsPrime(Factorial(NthPrime(n))-Factorial(n)+1)]; // Vincenzo Librandi, Aug 31 2015

Crossrefs

Cf. A261457.

Sequence in context: A134089 A136647 A306001 * A052456 A276991 A000532

Adjacent sequences: A261727 A261728 A261729 * A261731 A261732 A261733

Keyword

nonn,more

Author

Altug Alkan, Aug 30 2015

Extensions

a(4)-a(5) from Giovanni Resta, Aug 30 2015

Status

approved