login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A124083 Numbers k such that prime(k)!/prime(k)# + 1 is prime. 1
1, 2, 3, 60, 90 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(6) > 500 if it exists. - Felix Fröhlich, Sep 15 2019

LINKS

Table of n, a(n) for n=1..5.

EXAMPLE

1*2/2 +1 = 2 prime so a(1)=1 as 2=prime(1).

1*2*3/(2*3) +1 = 2 prime so a(2)=2 as 3=prime(2).

1*2*3*4*5/(2*3*5) +1 = 5 prime so a(3)=3 as 5=prime(3).

PROG

(PARI) isok(k) = isprime(prime(k)!/prod(i=1, k, prime(i)) + 1); \\ Michel Marcus, Sep 15 2019

CROSSREFS

Cf. A092435 (p!/p#), A124082.

Sequence in context: A154253 A097961 A145556 * A112098 A144545 A085326

Adjacent sequences:  A124080 A124081 A124082 * A124084 A124085 A124086

KEYWORD

nonn,more

AUTHOR

Pierre CAMI, Nov 25 2006

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 13 23:41 EDT 2021. Contains 343868 sequences. (Running on oeis4.)