Semiprimes formed by concatenating n, n, and 1 for n = 1, 2, 3,....

Terms

a(0) =111a(1) =221a(2) =551a(3) =771a(4) =11111a(5) =14141a(6) =15151a(7) =16161a(8) =19191a(9) =23231a(10) =24241a(11) =29291a(12) =30301a(13) =34341a(14) =36361a(15) =37371a(16) =38381a(17) =39391a(18) =42421a(19) =44441a(20) =47471a(21) =50501a(22) =53531a(23) =55551a(24) =56561a(25) =59591a(26) =62621a(27) =68681a(28) =70701a(29) =74741