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 A119036 #12 Sep 08 2022 08:45:25
%S A119036 1,2,4,24,77,141,778,1421,1435,1620,14220,15035,45453,148533,148546,
%T A119036 249122,471404,791597,4497399,2580747997,47180737658,148411814220,
%U A119036 244989930458,447283652733,1422190795997,2581981034024
%N A119036 Numbers k such that the k-th triangular number contains only digits {0,1,3}.
%H A119036 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr013.html">Tridigital Triangular Numbers</a>
%t A119036 Select[Range[2 10^7], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 3}] == {}&] (* _Vincenzo Librandi_, Oct 07 2015 *)
%o A119036 (Magma) [n: n in [1..2*10^7] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 3]]; // _Vincenzo Librandi_, Oct 07 2015
%Y A119036 Cf. A000217, A119035. See A119034 for a table of cross-references.
%K A119036 nonn,base
%O A119036 1,2
%A A119036 _Giovanni Resta_, May 10 2006