A136351 Primorial numbers p# such that p# + 1 is a prime.

1, 2, 6, 30, 210, 2310, 200560490130

Offset

1,2

Comments

This sequence is different from A121069 and A002110.

a(8) = A002110(75) has 154 digits and is too long to be listed. - R. J. Mathar, Jul 23 2008

Links

James C. McMahon, Table of n, a(n) for n = 1..10 (a(n) for n = 2..10 by Miles Englezou).

Formula

{A002110(j): A002110(j)+1 in A000040}. - R. J. Mathar, Jul 23 2008

a(n) = A002110(A014545(n)). - Michel Marcus, Apr 05 2021

a(n) = A018239(n) - 1. - James C. McMahon, May 08 2025

Example

a(6)=2310 is followed by prime 2311 whereas 30030 is not followed by a prime.

Mathematica

Select[FoldList[Times, 1, Prime[Range[18]]], PrimeQ[#+1]&] (* James C. McMahon, May 08 2025 *)

Prog

(PARI) S=[]; for(n=0, 80, k=vecprod(primes(n)); if(isprime(k+1), S=concat(S, k))); S \\ Miles Englezou, Oct 28 2024

Crossrefs

Cf. A002110, A014545, A018239, A121069, A136349, A136350, A136352.

Sequence in context: A058694 A336672 A046853 * A071290 A185693 A093449

Adjacent sequences: A136348 A136349 A136350 * A136352 A136353 A136354

Keyword

easy,nonn

Author

Enoch Haga, Dec 25 2007

Extensions

Changed a(1) from 4 to 2 and edited by R. J. Mathar, Jul 23 2008

a(1)=1 inserted by James C. McMahon, May 08 2025

Status

approved