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%I #11 Jul 13 2021 07:24:02
%S 284,3080,97680,9460126854061817544
%N Numbers k such that the k-th triangular number contains only digits {0,4,7}.
%C No other terms below 1.4*10^20.
%H G. Resta, <a href="http://www.numbersaplenty.com/tr/tr047.html">Tridigital Triangular Numbers</a>
%Y Cf. A000217, A218399. See A119034 for a table of cross-references.
%K base,nonn,more
%O 1,1
%A _Max Alekseyev_, Oct 28 2012
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