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 A038378 #27 Mar 04 2020 22:57:13
%S A038378 0,10,102,1023,10234,102345,1023456,10234567,102345678,1023456789
%N A038378 Integers which have more distinct digits than any smaller number.
%C A038378 Or: Smallest number with exactly n distinct digits. - _M. F. Hasler_, May 04 2017
%H A038378 S. Colton, <a href="http://www.cs.uwaterloo.ca/journals/JIS/colton/joisol.html">Refactorable Numbers - A Machine Invention</a>, J. Integer Sequences, Vol. 2, 1999, #2.
%H A038378 S. Colton, <a href="http://web.archive.org/web/20070831060523/http://www.dai.ed.ac.uk/homes/simonco/research/hr/">HR - Automatic Theory Formation in Pure Mathematics</a>
%t A038378 Prepend[NestList[FromDigits[Append[IntegerDigits[#],Last[Union[IntegerDigits[#]]]+1]]&,10,8],0] (* _Ivan N. Ianakiev_, May 10 2015 *)
%t A038378 Join[{0},Table[FromDigits[PadRight[{1,0},n,{1,0,2,3,4,5,6,7,8,9}]],{n,2,10}]] (* _Harvey P. Dale_, Sep 27 2016 *)
%o A038378 (PARI) A038378(n)=sum(i=1,n--,10^(n-i)*if(i>1,i,10)) \\ _M. F. Hasler_, May 04 2017
%Y A038378 Cf. A007809, A043537, A086069.
%K A038378 nonn,fini,full,base,nice
%O A038378 1,2
%A A038378 _N. J. A. Sloane_
%E A038378 Offset fixed by _Reinhard Zumkeller_, Aug 25 2009