login
This site is supported by donations to The OEIS Foundation.

 

Logo

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A076185 Numbers n such that n!! + 2 is prime. 18
0, 1, 3, 5, 7, 9, 21, 23, 27, 57, 75, 103, 169, 219, 245, 461, 695, 1169, 3597, 3637, 7495, 27743, 28799, 32501 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(25) > 50000. - Robert Price, Jan 18 2015

a(1)=0 since 0!!=1 and 1+2 = 3 is prime. - Robert Price, Jan 18 2015

LINKS

Table of n, a(n) for n=1..24.

C. K. Caldwell, The Prime Glossary, Multifactorial prime

C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75

Ken Davis, Status of Search for Multifactorial Primes.

Joe McLean, Interesting Sources of Probable Primes

The OpenPFGW Project, Primality Tester

MATHEMATICA

lst={}; Do[If[PrimeQ[n!!+2], AppendTo[lst, n]], {n, 0, 13^3}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 08 2008 *)

Select[Range[0, 33000], PrimeQ[#!!+2]&] (* Harvey P. Dale, Jul 28 2017 *)

CROSSREFS

Cf. A006882, A080778 and A076186, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.

Sequence in context: A003219 A030142 A179085 * A101813 A134719 A273519

Adjacent sequences:  A076182 A076183 A076184 * A076186 A076187 A076188

KEYWORD

nonn,more

AUTHOR

Zak Seidov, Nov 02 2002

EXTENSIONS

Edited and extended (n<4096) by Hugo Pfoertner, Jun 19 2003

One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 30 2007

a(22) - a(23) from Robert Price, Oct 17 2012

a(24) from Robert Price, Jan 18 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 20 03:34 EDT 2017. Contains 290823 sequences.