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

2, 3, 4, 14, 15, 17, 24, 41, 54, 77, 275, 447, 524, 574, 1546, 2132, 2711, 2804, 7994, 11684, 12073

Offset

1,1

Links

Table of n, a(n) for n=1..21.

Example

3 is a term 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

a(20)-a(21) from Michael S. Branicky, Jun 14 2024

Status

approved