%I #18 Jan 14 2019 17:30:19
%S 33,66,99,1212,1515,1818,2121,2424,2727,3030,3333,3636,3939,4242,4545,
%T 4848,5151,5454,5757,6060,6363,6666,6969,7272,7575,7878,8181,8484,
%U 8787,9090,9393,9696,9999,102102,105105,108108,111111,114114,117117,120120,123123
%N 3n concatenated with itself.
%t #*10^IntegerLength[#]+#&/@(3*Range[50]) (* _Harvey P. Dale_, Jan 14 2019 *)
%K nonn,base,easy
%O 1,1
%A _Larry Guindine_, Sep 30 2014
%E Definition edited by _N. J. A. Sloane_, Sep 30 2014
%E More terms from _Alois P. Heinz_, Sep 30 2014