A122719 Primes p such that (2p)!! - 1 is prime.

2, 3, 13, 41, 59, 97, 107, 421, 1663, 22159

Offset

1,1

Comments

a(n) are the primes from A091415[n] = {2,3,4,8,13,32,41,45,59,97,107,364,421,...} Numbers n such that n!*2^n - 1 is prime. Corresponding primes of the form (2p)!! - 1 are {3,5,270269,26226140915375977206881249, 58431212742946338570036120182498518593749,...}

No other terms up to 3000. - Stefan Steinerberger, Sep 09 2007

Links

Table of n, a(n) for n=1..10.

Mathematica

Select[Prime[Range[651]], PrimeQ[(2#)!!-1]&]

Crossrefs

Cf. A007749, A117141, A091415.

Sequence in context: A235615 A117528 A264042 * A106866 A278139 A280005

Adjacent sequences: A122716 A122717 A122718 * A122720 A122721 A122722

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Sep 23 2006

Extensions

a(9) from Stefan Steinerberger, Sep 09 2007

a(10) from Robert Price, Nov 26 2013

Status

approved