A091907 Numbers n such that (2*n)!/(2*n!)-1 is prime.

2, 3, 4, 14, 15, 17, 24, 41, 54, 77, 275, 447, 524, 574, 1546, 2132, 2711, 2804, 7994

Offset

1,1

Comments

a(20) > 10000. - Hugo Pfoertner, Jul 14 2019

Links

Table of n, a(n) for n=1..19.

Example

a(2)=3 because (2*3)!/(2*3!)-1=720/12-1=59 is prime.

Crossrefs

Cf. A091909.

Sequence in context: A067177 A171573 A039576 * A354075 A344313 A103048

Adjacent sequences: A091904 A091905 A091906 * A091908 A091909 A091910

Keyword

nonn,more,hard

Author

Hugo Pfoertner, Feb 10 2004

Extensions

a(15)-a(19) from Hugo Pfoertner, Jul 14 2019

Status

approved