A112855 Numbers n such that (2*n)!/n!+1 is prime.

1, 2, 5, 10, 24, 30, 72, 340, 379, 712, 1020, 1647, 3654, 7923

Offset

1,2

Comments

Next term is > 10000.

Links

Table of n, a(n) for n=1..14.

Mathematica

Select[Range[8000], PrimeQ[(2#)!/#!+1]&] (* Harvey P. Dale, Mar 23 2012 *)

Crossrefs

Cf. A112856 primes of the form (2*n)!/n!+1, A112853 (2*n)!/n!-1 is prime, A066726 (2*n)!/(n!)^2-1 is prime, A112859 (2*n)!/(n!)^2+1 is prime, A112861 (2*n)!/(2*(n!)^2)-1 is prime, A112863 (2*n)!/(2*(n!)^2)+1 is prime.

Sequence in context: A297074 A099963 A152784 * A361505 A299436 A049937

Adjacent sequences: A112852 A112853 A112854 * A112856 A112857 A112858

Keyword

hard,nonn

Author

Hugo Pfoertner, Sep 25 2005

Status

approved