OFFSET
1,2
MATHEMATICA
q[n_] := PrimeQ[Prime[n]*Product[Prime[i], {i, 1, n}] - 1]; Select[Range[500], q] (* Amiram Eldar, Jul 18 2021 *)
Module[{nn=500, p1, p2}, p1=Prime[Range[nn]]; p2=FoldList[Times, p1]; Select[Thread[ {p1, p2}], PrimeQ[ Times@@#-1]&][[;; , 1]]]//PrimePi (* Harvey P. Dale, May 21 2023 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Mar 22 2005
EXTENSIONS
a(14) from Amiram Eldar, Jul 18 2021
a(15) from Michael S. Branicky, May 28 2023
STATUS
approved