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%I #16 Mar 29 2023 19:56:41
%S 6,66,666,677766969666676,66799696699976679697696799766996696
%N Triangular numbers composed of digits {6,7,9}.
%C a(6) > 10^40. - _Tyler Busby_, Mar 29 2023
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr679.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119233(n)). - _Michel Marcus_, Mar 27 2023
%Y Cf. A000217, A053973, A119233. See A119033 for a table of cross-references.
%K nonn,base,more
%O 1,1
%A _Giovanni Resta_, May 10 2006
%E a(5) from _Max Alekseyev_, Mar 10 2009