A problem sending a sequence

Gerald McGarvey Gerald.McGarvey at comcast.net
Tue Nov 8 02:55:26 CET 2005

Two sequences related to this:

Primorial primes: primes p such that 1 + product of primes up to p is prime.

-1 + product of primes up to p is prime.

Gerald McGarvey

At 08:30 PM 11/7/2005, Tautócrona wrote:
>I'm trying to send the following sequence to the OEIS:
>Your name (required): Jose Brox
>Email address (required): tautocrona at terra.es
>New sequence
>initial terms here:
>Brief description or definition of sequence (required for a new sequence):
>The prime numbers n such that the primorial of n is surrounded by a pair 
>of twin primes.
>What is the value of the "index" or "subscript" of the initial term?
>Give formula, recurrence or generating function if known:
>a(n) is the n-th prime having the property that p#-1 and p#+1 are also primes
>Give an example:
>a(2) = 5 because 5#-1 = 209 and 5#+1 = 211 are both prime at the same 
>time, and 3 is the
>only prime less than 5 having this property.
>Jose Brox conjecture that this sequence is finite and that its last member 
>is 11. It has
>been verified up to n=10000 with the program below.
>Program to generate the sequence: (PARI)
>Select keywords:
>  nonn, hard, more
>The problem seems to be that the sequence has less than 4 elements listed. 
>But I couldn't
>find another member of the sequence and I conjecture that, indeed, the 
>sequence is finite
>and consist only of 3,5,11... but I can't mark the keywords "fini" and 
>"full" because I'm
>not sure at all about it.
>But I think the seq is interesting enough to get its place in the OEIS.
>Can NJAS put it by hand? Maybe is there a trick to upload seqs with less 
>than 4 terms if
>they are not known?
>Regards. Jose Brox
>ambroxius at terra.es
>MSN Messenger: artifex_ad_infinitum2 at hotmail.com

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