OFFSET
1,1
FORMULA
p, 2p-21 and 2p+21 all are positive primes.
MATHEMATICA
Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]
Select[Prime[Range[4, 500]], And@@PrimeQ[2#+{21, -21}]&] (* Harvey P. Dale, Dec 18 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Feb 16 2005
STATUS
approved