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A112855
Numbers n such that (2*n)!/n!+1 is prime.
5
1, 2, 5, 10, 24, 30, 72, 340, 379, 712, 1020, 1647, 3654, 7923
OFFSET
1,2
COMMENTS
Next term is > 10000.
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
KEYWORD
hard,nonn
AUTHOR
Hugo Pfoertner, Sep 25 2005
STATUS
approved