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 A180409 #6 Jun 02 2025 03:03:54
%S A180409 1,2,3,4,5,6,7,8,9,10,1,12,13,14,15,16,17,18,19,20,12,2,23,24,25,26,
%T A180409 27,28,29,30,13,23,3,34,35,36,37,38,39,40,14,24,34,4,45,46,47,48,49,
%U A180409 50,15,25,35,45,5,56,57,58,59,60,16,26,36,46,56,6
%N A180409 Unique digits used in n in numerical order (with 0 last).
%F A180409 a(n) = 1234567890 after any digits not appearing in n are removed
%e A180409 a(93077) = 3790. Seven is only used once and the digits are sorted with zero last
%t A180409 udno[n_]:=Module[{c=Union[IntegerDigits[n]]},FromDigits[If[First[c] == 0, RotateLeft[ c],c]]]; Array[udno,70] (* _Harvey P. Dale_, Dec 23 2015 *)
%K A180409 easy,nonn,base
%O A180409 1,2
%A A180409 _Dominick Cancilla_, Sep 02 2010