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

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A051915 Numbers n such that 2*n! + 1 is a prime. 10
0, 1, 2, 3, 5, 12, 18, 35, 51, 53, 78, 209, 396, 4166, 9091, 9587, 13357, 15917, 17652, 46127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Used PrimeForm to prove primality for n = 4166 (classical N-1 test). - David Radcliffe, May 28 2007

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

n=5 is here because 2*5! + 1 = 241 is a prime.

MATHEMATICA

Select[Range[0, 400], PrimeQ[2*#! + 1] &] (* Vladimir Joseph Stephan Orlovsky, Feb 13 2012 *)

PROG

(MAGMA) [n: n in [0..1000] | IsPrime(2*Factorial(n) +1)]; // Vincenzo Librandi, Feb 21 2015

CROSSREFS

Cf. A051888, A076133, A076134, A076679.

Sequence in context: A002139 A140489 A193776 * A064688 A089891 A004689

Adjacent sequences:  A051912 A051913 A051914 * A051916 A051917 A051918

KEYWORD

nonn,more

AUTHOR

Labos Elemer, Dec 18 1999

EXTENSIONS

4166 from David Radcliffe, May 28 2007

More terms from Serge Batalov, Feb 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 December 3 03:54 EST 2016. Contains 278698 sequences.