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 A119042 #13 Sep 08 2022 08:45:25
%S A119042 1,3,4,11,36,141,179,363,1095,3633,4473,4704,36333,44758,46079,46904,
%T A119042 57620,1414920,1460141,4474371,14560288,348310541,1822424761720,
%U A119042 34670191840011,471172177895936,4472359691719799
%N A119042 Numbers k such that the k-th triangular number contains only digits {0,1,6}.
%C A119042 Next term exceeds 1.4*10^16.
%H A119042 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr016.html">Tridigital Triangular Numbers</a>
%t A119042 Select[Range[2 10^7], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 6}] == {} &] (* _Vincenzo Librandi_, Dec 25 2015 *)
%o A119042 (Magma) [n: n in [1..2*10^7] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 6]]; // _Vincenzo Librandi_, Dec 25 2015
%Y A119042 Cf. A000217, A119041. See A119034 for a table of cross-references.
%K A119042 nonn,base,more
%O A119042 1,2
%A A119042 _Giovanni Resta_, May 10 2006