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A173664 Sums of 2 primes that are not product of 2 primes.

%I A173664 #22 Feb 09 2013 21:48:54
%S A173664 5,7,8,12,13,16,18,19,20,24,28,30,31,32,36,40,42,43,44,45,48,50,52,54,
%T A173664 56,60,61,63,64,66,68,70,72,73,75,76,78,80,81,84,88,90,92,96,98,99,
%U A173664 100,102,103,104,105,108,109,110,112,114,116,120,124,126
%N A173664 Sums of 2 primes that are not product of 2 primes.
%H A173664 Alois P. Heinz, <a href="/A173664/b173664.txt">Table of n, a(n) for n = 1..1000</a>
%F A173664 A014091 \ A001358. - _R. J. Mathar_, Nov 24 2010
%p A173664 a:= proc(n) option remember; local k;
%p A173664       if n=1 then 5
%p A173664       else for k from a(n-1)+1 do
%p A173664              if add (i[2], i=ifactors(k)[2])=2 then next fi;
%p A173664              if irem (k, 2)=0 or isprime (k-2) then break fi
%p A173664            od; k
%p A173664       fi
%p A173664     end:
%p A173664 seq (a(n), n=1..60);  # _Alois P. Heinz_, Nov 24 2010
%t A173664 Select[Union[Flatten[Table[Prime[i] + Prime[j], {i, 25}, {j, 25}]]], PrimeOmega[#] != 2 &] (* _Alonso del Arte_, Feb 08 2013 *)
%o A173664 (PARI) is(n)=if(n%2,isprime(n-2)&&bigomega(n)!=2,n>2&&!isprime(n/2)) \\ above 4 * 10^18, conditional on the Goldbach conjecture _Charles R Greathouse IV_, Feb 09 2013
%Y A173664 Cf. A157931, A089268.
%K A173664 nonn
%O A173664 1,1
%A A173664 _Juri-Stepan Gerasimov_, Nov 24 2010
%E A173664 More terms from _Alois P. Heinz_, Nov 24 2010