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 A036786 #11 Aug 09 2017 00:16:11
%S A036786 10,50,100,101,105,110,150,200,400,500,501,505,510,550,600,900,1000,
%T A036786 1001,1002,1004,1005,1006,1009,1010,1011,1015,1020,1040,1050,1051,
%U A036786 1055,1060,1090,1100,1101,1105,1110,1150,1200,1400,1500,1501,1505,1510,1550
%N A036786 Length of Roman notation for n < length of decimal representation.
%H A036786 Nathaniel Johnston, <a href="/A036786/b036786.txt">Table of n, a(n) for n = 1..55</a> (complete up to 3999)
%F A036786 A006968(a(n)) < A055642(a(n)). - _Reinhard Zumkeller_, Apr 20 2013
%e A036786 1000 = M is shorter in Roman numerals, so 1000 is in this sequence.
%p A036786 for n from 1 to 3999 do if(length(convert(n,roman)) < length(n))then printf("%d, ",n): fi: od: # _Nathaniel Johnston_, May 18 2011
%t A036786 Select[Range[2000],StringLength[IntegerString[#,"Roman"]]<IntegerLength[ #]&] (* _Harvey P. Dale_, Feb 10 2015 *)
%o A036786 (Haskell)
%o A036786 a036786 n = a036786_list !! (n-1)
%o A036786 a036786_list = [x | x <- [1..], a006968 x < a055642 x]
%o A036786 -- _Reinhard Zumkeller_, Apr 20 2013
%Y A036786 Cf. A036787, A036788.
%K A036786 nonn,nice,easy,base
%O A036786 1,1
%A A036786 _J. H. Conway_
%E A036786 Corrected by Larry Reeves (larryr(AT)acm.org), Sep 25 2000