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%I #10 Jul 13 2021 07:28:05
%S 1,2,13,621,4458,489884458,632318261,893464178,16684802253,
%T 1621069592578,2502478528946,250255842662341,1543458022195053,
%U 527851115257700546
%N Numbers k such that the k-th triangular number contains only digits {1,3,9}.
%H G. Resta, <a href="http://www.numbersaplenty.com/tr/tr139.html">Tridigital Triangular Numbers</a>
%Y Cf. A000217, A119121. See A119034 for a table of cross-references.
%K nonn,base,more
%O 1,2
%A _Giovanni Resta_, May 10 2006
%E a(14) from _Max Alekseyev_, Oct 14 2012
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