Lucky numbers that are concatenations of a number k with itself.

Terms

a(0) =33a(1) =99a(2) =2121a(3) =2323a(4) =5151a(5) =5959a(6) =6363a(7) =7171a(8) =7575a(9) =8787a(10) =8989a(11) =9999a(12) =105105a(13) =111111a(14) =117117a(15) =123123a(16) =129129a(17) =135135a(18) =143143a(19) =147147a(20) =153153a(21) =171171a(22) =173173a(23) =177177a(24) =191191a(25) =201201a(26) =237237a(27) =243243a(28) =255255a(29) =263263