OFFSET
1,1
COMMENTS
Corresponding primes are 7, 13, 41, 181, 1009, 453601, ...
EXAMPLE
3 is a term because 2*3 + 1 = 7 is prime.
4 is a term because 1*3*4 + 1 = 13 is prime.
5 is a term because 1*2*4*5 + 1 = 41 is prime.
6 is a term because 1*2*3*5*6 + 1 = 181 is prime.
7 is a term because 1*2*3*4*6*7 + 1 = 1009 is prime.
MATHEMATICA
Select[Range[3, 2000], PrimeQ[( #! / (# - 2) + 1)] &] (* Vincenzo Librandi, Apr 07 2016 *)
PROG
(PARI) lista(nn) = for(n=3, nn, if(ispseudoprime(n!/(n-2)+1), print1(n, ", ")));
(PFGW) ABC2 $a!/($a-2) + 1
a: from 3 to 100000
(Magma) [n: n in [3..500] | IsPrime(Factorial(n) div (n-2) + 1)]; // Vincenzo Librandi, Apr 07 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Apr 05 2016
EXTENSIONS
a(23) from Charles R Greathouse IV, Apr 05 2016
a(24)-a(27) from Charles R Greathouse IV, Apr 06 2016
a(28)-a(32) from Charles R Greathouse IV, Apr 18 2016
a(33) from Charles R Greathouse IV, Apr 30 2016
a(34) from Charles R Greathouse IV, May 09 2016
STATUS
approved