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 A119063 #11 Jul 14 2025 11:17:17
%S A119063 3,6,36,66,300,630,666,3003,66066,333336,600060,630003,3306306,
%T A119063 30330366,330360660,6603360660,63630666636636,633663606306030,
%U A119063 63033033630030366,66000033300360030336,33363363630036306006003,363003633036606030300000,663300330303660363306006
%N A119063 Triangular numbers composed of digits {0,3,6}.
%H A119063 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr036.html">Tridigital Triangular Numbers</a>
%F A119063 a(n) = A000217(A119064(n)). - _Michel Marcus_, Mar 22 2023
%t A119063 Select[FromDigits/@Tuples[{0,3,6},12],OddQ[Sqrt[8#+1]]&]//Rest (* The program generates the first 16 terms of the sequence. *) (* _Harvey P. Dale_, Jul 14 2025 *)
%Y A119063 Cf. A000217, A058432, A119064. See A119033 for a table of cross-references.
%K A119063 nonn,base
%O A119063 1,1
%A A119063 _Giovanni Resta_, May 10 2006
%E A119063 a(22)-a(23) from _Tyler Busby_, Mar 22 2023