%I #11 Mar 31 2023 03:20:41

%S 9,10,3390,38589,12453549,3080826336474,298253071929010,

%T 33089502135135685

%N Numbers k such that the k-th triangular number contains only digits {4,5,7}.

%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr457.html">Tridigital Triangular Numbers</a>.

%Y Cf. A000217, A119204. See A119034 for a table of cross-references.

%K nonn,base,more

%O 1,1

%A _Giovanni Resta_, May 10 2006

%E a(8) from _Tyler Busby_, Mar 31 2023