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%I #10 Mar 29 2023 05:02:12
%S 1,3,88831,1188111,38311881,11313313831,83388881331381,
%T 881388838113181838838811,8138133831331381318318881,
%U 183113183318838311383311313311,133831381813113188111133181833111,31188113313888818318833183383131131
%N Triangular numbers composed of digits {1,3,8}.
%C No other terms below 10^41. - _Tyler Busby_, Mar 28 2023
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr138.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119120(n)). - _Tyler Busby_, Mar 28 2023
%Y Cf. A000217, A053895, A119120. See A119033 for a table of cross-references.
%K nonn,base
%O 1,2
%A _Giovanni Resta_, May 10 2006
%E Two more terms from _Max Alekseyev_, May 12 2009