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 A260214 #40 Aug 04 2015 01:13:09
%S A260214 0,10,105,1035,10296,102378,1024596,10348975,102738945,1062489753
%N A260214 a(n) is the first triangular number whose decimal representation uses n distinct digits.
%H A260214 Anders Hellström, <a href="/A260214/b260214.txt">Table of n, a(n) for n = 1..10</a>
%F A260214 a(n) = A255678(n)*(A255678(n)+1)/2.
%t A260214 # (# + 1)/2 & /@ {0, 4, 14, 45, 143, 452, 1431, 4549, 14334, 46097} (* terms in A255678 *) (* _Robert G. Wilson v_, Jul 21 2015 *)
%o A260214 (PARI) number_of_distinct_digits(m) = if(m==0,1,#vecsort(digits(m), , 8))
%o A260214 a(n)=my(m=0); while(!(number_of_distinct_digits(m*(m+1)/2)==n), m++); m*(m+1)/2;
%o A260214 first(m)=vector(m, n, a(n)) \\m<=10 /* _Anders Hellström_, Aug 03 2015 */
%Y A260214 Cf. A000217, A043537, A118668, A255678.
%K A260214 nonn,base,fini,full
%O A260214 1,2
%A A260214 _Anders Hellström_, Jul 19 2015