The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #10 Apr 06 2023 20:01:20
%S 990,4009490400090,990440044904409490,9900404040400404004090
%N Triangular numbers composed of digits {0,4,9}.
%C a(5) > 10^40. - _Tyler Busby_, Mar 28 2023
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr049.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119078(n)). - _Tyler Busby_, Mar 28 2023
%Y Cf. A000217, A058444, A119078. See A119033 for a table of cross-references.
%K nonn,base,more
%O 1,1
%A _Giovanni Resta_, May 10 2006