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%I #21 Mar 30 2023 23:34:32
%S 6,66,406,666,66066,446040,600060,46046406,440466040,4040600460,
%T 6604444400406,4440066066400004040,644006046066000066046,
%U 44464646466606404046664666,464440406444064040044646006604604066,660466006640066446666000606004066646,60404640400640406040004460664400044060
%N Triangular numbers composed of digits {0,4,6}.
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr046.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119074(n)). - _Tyler Busby_, Mar 27 2023
%t Rest[Select[FromDigits/@Tuples[{0, 4, 6}, 10], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &]] (* _Vincenzo Librandi_, Dec 18 2015 *)
%o (Magma) [t: n in [1..2*10^7] | Set(Intseq(t)) subset {0,4,6} where t is n*(n+1) div 2]; // _Vincenzo Librandi_, Dec 18 2015
%Y Cf. A000217, A058438, A119074.
%Y See A119033 for a table of cross-references.
%K nonn,base
%O 1,1
%A _Giovanni Resta_, May 10 2006
%E a(15)-a(16) from _Max Alekseyev_, May 10 2009
%E a(17) from _Tyler Busby_, Mar 27 2023
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