A089130 Primes of the form (n! + 2)/2.

2, 13, 61, 2521, 20161, 3113510401, 10461394944001, 132626429906095529318154240000001, 30207631531686917818677566034256998753632256000000001

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..13

Mathematica

s=""; For[i=1, i<5^2, If[PrimeQ[(i!+2)/2], s=s<>ToString[(i!+2)/2]<>", "]; i++ ]; Print[s] (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)
Select[Table[(n!+2)/2, {n, 0, 100}], PrimeQ] (* Vincenzo Librandi, Dec 07 2011 *)

Prog

(PARI) nfactp2d2(n) = { for(x=1, n, y=floor((x!+ 2)/2); if(isprime(y), print1(y", ")) ) }
(Magma) [ a: n in [1..50] | IsPrime(a) where a is (Factorial(n)+2) div 2 ];

Crossrefs

Cf. A082672.

Sequence in context: A205532 A294052 A353177 * A081340 A211067 A296435

Adjacent sequences: A089127 A089128 A089129 * A089131 A089132 A089133

Keyword

nonn

Author

Cino Hilliard, Dec 05 2003

Status

approved