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%I #14 Mar 28 2023 15:08:37
%S 45,55,5747745,744574755,77545447574475,4745745457757444544544575,
%T 44477447457545755547775754555,547457575775574544754447747777455
%N Triangular numbers composed of digits {4,5,7}.
%C a(8) > 10^40. - _Tyler Busby_, Mar 28 2023
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr457.html">Tridigital Triangular Numbers</a>.
%F a(n) = A000217(A119205(n)). - _Jon E. Schoenfield_, Mar 27 2023
%Y Cf. A000217, A053951, A119205. See A119033 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 28 2023