%I #15 Jan 18 2021 02:40:41
%S 9,21,39,49,57,87,91,111,129,133,159,169,183,203,213,237,247,259,267,
%T 301,303,321,339,361,371,377,393,417,427,453,481,489,497,519,543,551,
%U 553,559,579,597,623,669,687,689,703,707,717,749,753,789,791,793,813,817
%N Numbers of the form prime(x) * prime(y) where x and y are both even.
%F Numbers m such that A001222(m) = 2 and A195017(m) = -2. - _Peter Munn_, Jan 17 2021
%e The sequence of terms together with their prime indices begins:
%e 9: {2,2} 237: {2,22} 481: {6,12}
%e 21: {2,4} 247: {6,8} 489: {2,38}
%e 39: {2,6} 259: {4,12} 497: {4,20}
%e 49: {4,4} 267: {2,24} 519: {2,40}
%e 57: {2,8} 301: {4,14} 543: {2,42}
%e 87: {2,10} 303: {2,26} 551: {8,10}
%e 91: {4,6} 321: {2,28} 553: {4,22}
%e 111: {2,12} 339: {2,30} 559: {6,14}
%e 129: {2,14} 361: {8,8} 579: {2,44}
%e 133: {4,8} 371: {4,16} 597: {2,46}
%e 159: {2,16} 377: {6,10} 623: {4,24}
%e 169: {6,6} 393: {2,32} 669: {2,48}
%e 183: {2,18} 417: {2,34} 687: {2,50}
%e 203: {4,10} 427: {4,18} 689: {6,16}
%e 213: {2,20} 453: {2,36} 703: {8,12}
%p q:= n-> (l-> add(i[2], i=l)=2 and andmap(i->
%p numtheory[pi](i[1])::even, l))(ifactors(n)[2]):
%p select(q, [$1..1000])[]; # _Alois P. Heinz_, Nov 23 2020
%t Select[Range[100],PrimeOmega[#]==2&&OddQ[Times@@(1+PrimePi/@First/@FactorInteger[#])]&]
%Y A338910 is the odd instead of even version.
%Y A339004 is the squarefree case.
%Y A001221 counts distinct prime indices.
%Y A001222 counts prime indices.
%Y A001358 lists semiprimes, with odd/even terms A046315/A100484.
%Y A006881 lists squarefree semiprimes, with odd/even terms A046388/A100484.
%Y A338899, A270650, A270652 list prime indices of squarefree semiprimes.
%Y A289182/A115392 list the positions of odd/even terms of A001358.
%Y A300912 lists semiprimes with relatively prime indices.
%Y A318990 lists semiprimes with divisible indices.
%Y A338904 groups semiprimes by weight.
%Y A338906/A338907 list semiprimes of even/odd weight.
%Y A338909 lists semiprimes with non-relatively prime indices.
%Y A338912 and A338913 list prime indices of semiprimes, with product A087794, sum A176504, and difference A176506.
%Y Cf. A005117, A037143, A055684, A056239, A065516, A112798, A128301, A195017, A320655, A320732, A320892, A338898, A339002, A339003.
%K nonn
%O 1,1
%A _Gus Wiseman_, Nov 20 2020