A112853 - OEIS

A112853

Numbers k such that (2*k)!/k!-1 is prime.

2, 6, 14, 25, 114, 188, 193, 361, 712, 1767, 3195, 4995, 5682, 6485, 9937

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OFFSET

1,1

COMMENTS

Next term is > 9680.

LINKS

Table of n, a(n) for n=1..15.

MATHEMATICA

Select[Range[7000], PrimeQ[(2#)!/#!-1]&] (* James C. McMahon, Jun 12 2024 *)

CROSSREFS

Cf. A112854 primes of the form (2*n)!/n!-1, A112855 (2*n)!/n!+1 is prime, A066726 (2*n)!/(n!)^2-1 is prime, A066699 (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: A106353 A002703 A230978 * A176752 A140759 A102486

Adjacent sequences: A112850 A112851 A112852 * A112854 A112855 A112856

KEYWORD

hard,more,nonn

AUTHOR

Hugo Pfoertner, Sep 25 2005

EXTENSIONS

a(15) from Michael S. Branicky, Jun 12 2024

STATUS

approved