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%I #13 Mar 31 2023 13:21:15
%S 1,10,171,1711,1770,10011,111117701071,17170010070077710,
%T 101711101707777771,701000700077010700,1701111717707771071,
%U 10010107100007777700,101770070070071771070,170107111111710707070,1177170070777107111711,70071707101001717077017171
%N Triangular numbers composed of digits {0,1,7}.
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr017.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119044(n)). - _Tyler Busby_, Mar 31 2023
%t Select[FromDigits/@Tuples[{0,1,7},12],OddQ[Sqrt[8#+1]]&] (* The program generates the first 8 terms of the sequence. *) (* _Harvey P. Dale_, Sep 06 2022 *)
%Y Cf. A000217, A058420, A119044. See A119033 for a table of cross-references.
%K nonn,base
%O 1,2
%A _Giovanni Resta_, May 10 2006
%E a(15)-a(16) from _Tyler Busby_, Mar 22 2023
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