OFFSET
1,2
PROG
(PARI) isok(n) = {my(pp=prod(k=1, n, prime(k))); isprime(pp*prime(n+1) - pp -1); } \\ Michel Marcus, Sep 20 2019
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Mar 19 2007
EXTENSIONS
a(17) from Michael S. Branicky, Oct 06 2024
STATUS
approved