%I #13 Jan 04 2024 15:12:26
%S 1,21,231,12403,24531,235641,2467531,13862745,153694278,10429651378,
%T 1017139458621,101114872391625,10111496127133528,1011137441915312286,
%U 101111293764315411825,10111111491815764232356,1011111155214617733491628,101111111617874325294116835
%N Smallest triangular number containing all the digits of numbers from 1 to n.
%C For a(10) and higher, all duplicated digits must be in the term (for example a(10) has two 1's).
%C Conjecture: except for a(4), the digits of a(n) are exactly all the digits of numbers from 1 to n. - _Chai Wah Wu_, May 18 2020
%H Chai Wah Wu, <a href="/A069601/b069601.txt">Table of n, a(n) for n = 1..29</a>
%e a(5) = 219453 = T(662) contains digits 1, 2, 3, 4 and 5.
%Y Cf. A088628, A069600.
%K nonn,base
%O 1,2
%A _Amarnath Murthy_, Mar 25 2002
%E Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jan 24 2003
%E a(15)-a(18) from _Chai Wah Wu_, May 18 2020