OFFSET
1,1
COMMENTS
Conjecture: sequence is finite.
No more terms in the first 300 primorials. - David Wasserman, Jul 25 2005
Search extended to first 700 primorials by Michael De Vlieger, Aug 31 2016
Search extended to first 3000 primorials. - Josey Stevens, Aug 10 2021
The first more than 230000 primorial numbers k have been checked for whether k-1 or k+1 or both are primes. See links. If another term k exists, it is over about 10^1400000. - Jeppe Stig Nielsen, Oct 19 2021
LINKS
Chris K. Caldwell, The Top Twenty: Primorial, in the Prime Pages.
EXAMPLE
210 = primorial(4) is not a member as 209 is composite.
MAPLE
f:= proc(n)
local P;
P:= mul(seq(ithprime(i), i=1..n));
if isprime(P+1) and isprime(P-1) then P else NULL fi
end proc:
map(f, [$1..300]); # Robert Israel, Aug 31 2016
MATHEMATICA
Select[Times @@ # & /@ Prime@ Range@ Range@ 700, Times @@ Boole@ PrimeQ@ {# - 1, # + 1} == 1 &] (* Michael De Vlieger, Aug 31 2016 *)
Select[FoldList[Times, Prime[Range[20]]], AllTrue[#+{1, -1}, PrimeQ]&] (* Harvey P. Dale, Mar 31 2023 *)
PROG
(PARI) lista(nn) = for (n=1, nn, pr = prod(i=1, n, prime(i)); if (isprime(pr-1) && isprime(pr+1), print1(pr, ", "))); \\ Michel Marcus, Aug 31 2016
CROSSREFS
KEYWORD
more,nonn,bref
AUTHOR
Amarnath Murthy, Sep 27 2003
EXTENSIONS
Corrected by Ray Chandler, Sep 28 2003
STATUS
approved