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Products of two primes p and q such that (p*q)^2 + p^2 - q^2 and (p*q)^2 - p^2 + q^2 are both prime.
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%I #3 Mar 30 2012 17:21:00

%S 6,14,22,33,35,38,62,69,74,85,115,119,146,159,214,219,237,267,301,335,

%T 339,469,511,519,537,542,559,566,573,591,597,634,718,721,737,794,803,

%U 851,878,917,933,1003,1007,1042,1059,1099,1219,1226,1241,1271,1294,1299

%N Products of two primes p and q such that (p*q)^2 + p^2 - q^2 and (p*q)^2 - p^2 + q^2 are both prime.

%C The two primes generated from p and q are sometimes called flip-flap twin primes. There is probably an infinity of them.

%e a(2) = 14 since (2*7)^2 + 2^2 - 7^2 = 151 and (2*7)^2 - 2^2 + 7^2 = 241 are both primes.

%K easy,nonn

%O 1,1

%A _Olivier GĂ©rard_, Feb 19 2003