%I
%S 13,19,29,31,41,59,79,89,101,109,131,179,211,239,241,271,311,331,349,
%T 409,421,449,499,509,521,541,601,619,701,751,821,839,881,1009,1091,
%U 1181,1201,1319,1321,1399,1429,1459,1489,1531,1571,1619,1801,1949,1951
%N Primes p such that both 2p +/ 21 are primes.
%F p, 2p21 and 2p+21 all are positive primes.
%t Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2#  21] &]
%t Select[Prime[Range[4,500]],And@@PrimeQ[2#+{21,21}]&] (* _Harvey P. Dale_, Dec 18 2012 *)
%Y Cf. A103802, A103803.
%K nonn
%O 1,1
%A _Zak Seidov_, Feb 16 2005
