%I
%S 1,10,10011,10440,41041,41001040,141044410,1010004040,4104044101,
%T 14041444410,114011410040100,440404440401100,1041401040044401,
%U 40114114410110140,14001400401400441011,1040410404040110411004140
%N Triangular numbers composed of digits {0,1,4}.
%H G. Resta, <a href="http://www.numbersaplenty.com/tr/tr014.html">Tridigital Triangular Numbers</a>
%t Rest[Select[FromDigits/@Tuples[{0, 1, 4}, 12], IntegerQ[(Sqrt[8 # + 1]  1)/2] &]] (* _Vincenzo Librandi_, Dec 18 2015 *)
%o (MAGMA) [t: n in [1..2*10^7]  Set(Intseq(t)) subset {0,1,4} where t is n*(n+1) div 2]; // _Vincenzo Librandi_, Dec 18 2015
%Y Cf. A000217, A058414, A119038. See A119033 for a table of crossreferences.
%K nonn,base
%O 1,2
%A _Giovanni Resta_, May 10 2006
