Semiprimes that are semiprimes turned upside-down.

Terms

a(0) =6a(1) =9a(2) =69a(3) =106a(4) =111a(5) =119a(6) =611a(7) =669a(8) =689a(9) =698a(10) =699a(11) =818a(12) =866a(13) =869a(14) =901a(15) =998a(16) =1011a(17) =1101a(18) =1111a(19) =1198a(20) =1199a(21) =1661a(22) =1681a(23) =1689a(24) =1691a(25) =1819a(26) =1891a(27) =1919a(28) =1961a(29) =1966