A136352 Primorials P for which neither P-1 nor P+1 is prime.

510510, 9699690, 223092870, 6469693230, 7420738134810, 13082761331670030, 614889782588491410, 32589158477190044730, 1922760350154212639070, 117288381359406970983270, 7858321551080267055879090

Offset: 1

Author

Enoch Haga, Dec 25 2007

Keywords

• easy
• nonn

Comments

This sequence is different from A121069 and A002110.

For almost all primes p, p# is in this sequence by Brun's theorem. - Charles R Greathouse IV, Sep 14 2015

Examples

			13# = 30030 is preceded by a prime but is not followed by a prime. 17# = 510510 is neither preceded nor followed by a prime.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..350

Crossrefs

Cf. A136349, A136350, A136351, A002110, A121069.

Programs

Mathematica

Select[FoldList[Times, 1, Prime[Range[19]]],!PrimeQ[#+1]&&!PrimeQ[#-1]&] (* James C. McMahon, May 08 2025 *)

Formula

Compute P = product of the first k primes. If P is neither preceded nor followed by a prime add P to the sequence.

Extensions

Edited by and more terms from Charles R Greathouse IV, Sep 29 2008