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%I #11 Mar 14 2023 12:59:30
%S 1,10,91,190,990,10011,19110,19900,90100,1911990,1991010,1999000,
%T 99991011,199110990,199910010,199990000,901999101,1000900911,
%U 1111019091,19991100990,19999100010,19999900000,1999911000990,1999991000010,1999999000000,11109109109010
%N Triangular numbers composed of digits {0,1,9}.
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr019.html">Tridigital Triangular Numbers</a>
%F a(n) = A000217(A119048(n)). - _Michel Marcus_, Mar 14 2023
%Y Cf. A000217, A119048. See A119033 for a table of cross-references.
%K nonn,base
%O 1,2
%A _Giovanni Resta_, May 10 2006
%E a(24)-a(26) from _Tyler Busby_, Mar 14 2023
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