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%I #7 Mar 28 2023 17:46:21
%S 3,300,703,3003,300700,7777333333770,30770737700703,7707033303703300,
%T 77300377037737303073770,3073770307037370707370300003,
%U 33000770070773300000703773730,770037773370037377077730333003
%N Triangular numbers composed of digits {0,3,7}.
%C a(13) > 10^41. - _Tyler Busby_, Mar 28 2023
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr037.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119066(n)). - _Tyler Busby_, Mar 28 2023
%Y Cf. A000217, A119066. See A119033 for a table of cross-references.
%K nonn,base
%O 1,1
%A _Giovanni Resta_, May 10 2006