This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A119040 #13 Sep 08 2022 08:45:25
%S A119040 1,4,5,10,14,100,101,141,173,458,1000,1001,1005,1010,4475,10000,10001,
%T A119040 10005,10010,10100,10110,10114,14869,45858,54873,100000,100001,100005,
%U A119040 100010,100100,100101,101000,101005,1000000,1000001,1000005,1000010
%N A119040 Numbers k such that the k-th triangular number contains only digits {0,1,5}.
%H A119040 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr015.html">Tridigital Triangular Numbers</a>
%t A119040 Select[Range[2 10^6], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 5}] == {} &] (* _Vincenzo Librandi_, Dec 25 2015 *)
%o A119040 (Magma) [n: n in [1..2*10^6] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 5]]; // _Vincenzo Librandi_, Dec 25 2015
%Y A119040 Cf. A000217, A119039. See A119034 for a table of cross-references.
%K A119040 nonn,base
%O A119040 1,2
%A A119040 _Giovanni Resta_, May 10 2006