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 A119152 #15 May 03 2023 09:14:38
%S A119152 3,55,253,325,5253,255255,2235555,2355535,3252525,222552253,
%T A119152 225323523253,33533553332223253,523355323323222253,
%U A119152 252235353552533225335,22323332525535322225335,223533355523232355353232325353525335
%N A119152 Triangular numbers composed of digits {2,3,5}.
%C A119152 a(17) > 10^40. - _Tyler Busby_, Mar 28 2023
%H A119152 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr235.html">Tridigital Triangular Numbers</a>.
%F A119152 a(n) = A000217(A119153(n)). - _Tyler Busby_, Mar 28 2023
%Y A119152 Cf. A000217, A053919, A119153. See A119033 for a table of cross-references.
%K A119152 nonn,base
%O A119152 1,1
%A A119152 _Giovanni Resta_, May 10 2006
%E A119152 a(16) from _Tyler Busby_, Mar 28 2023