This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A069601 #13 Jan 04 2024 15:12:26 %S A069601 1,21,231,12403,24531,235641,2467531,13862745,153694278,10429651378, %T A069601 1017139458621,101114872391625,10111496127133528,1011137441915312286, %U A069601 101111293764315411825,10111111491815764232356,1011111155214617733491628,101111111617874325294116835 %N A069601 Smallest triangular number containing all the digits of numbers from 1 to n. %C A069601 For a(10) and higher, all duplicated digits must be in the term (for example a(10) has two 1's). %C A069601 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 A069601 Chai Wah Wu, <a href="/A069601/b069601.txt">Table of n, a(n) for n = 1..29</a> %e A069601 a(5) = 219453 = T(662) contains digits 1, 2, 3, 4 and 5. %Y A069601 Cf. A088628, A069600. %K A069601 nonn,base %O A069601 1,2 %A A069601 _Amarnath Murthy_, Mar 25 2002 %E A069601 Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jan 24 2003 %E A069601 a(15)-a(18) from _Chai Wah Wu_, May 18 2020