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Numbers k such that the k-th triangular number contains only digits {2,4,5}.
2

%I #12 Jul 13 2021 07:25:56

%S 9,10,225,714,6714,22114,2119209,2211449,102523609,942573334,

%T 95336514049,3333030289167658390

%N Numbers k such that the k-th triangular number contains only digits {2,4,5}.

%C Next term exceeds 1.4*10^20.

%H G. Resta, <a href="http://www.numbersaplenty.com/tr/tr245.html">Tridigital Triangular Numbers</a>

%Y Cf. A000217, A119158. See A119034 for a table of cross-references.

%K nonn,base,more

%O 1,1

%A _Giovanni Resta_, May 10 2006

%E a(12) from _Max Alekseyev_, Aug 19 2013