OFFSET
1,1
COMMENTS
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
PROG
(PARI) a(n) = !(n %7) && isprime(n+1) && isprime(n-1); \\ Michel Marcus, Oct 11 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Apr 01 2007
STATUS
approved