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 A142958 #14 Dec 08 2017 23:57:15
%S A142958 3,7,12,14,16,19,21,25,30,41,45,52,54,56,59,61,65,70,91,95,102,104,
%T A142958 106,109,111,115,120,140,151,155,160,190,201,205,210,250,300,401,405,
%U A142958 410,450,502,504,506,509,511,515,520,540,551,555,560,590,601,605,610,650
%N A142958 Roman numerals containing three letters (i.e., III, VII, XII, XIV, ...).
%H A142958 Nathaniel Johnston, <a href="/A142958/b142958.txt">Table of n, a(n) for n = 1..93</a> (complete up to 3999)
%H A142958 Ron Barnette's Zeno's Coffeehouse, <a href="http://www.ronbarnette.com/Zeno/result56.htm">Challenge #56 Result</a>. Mentions this sequence.
%H A142958 Gerard Schildberger, <a href="/A006968/a006968.txt">The first 3999 numbers in Roman numerals</a>.
%p A142958 for n from 1 to 3999 do if(length(convert(n, roman)) = 3)then printf("%d, ", n): fi: od: # _Nathaniel Johnston_, May 18 2011
%t A142958 (* go to the hyperlink and assign the first 700 Roman numerals to the variable 'lst' so that lst = {I, II, III, ..., DCXCVIII, DCXCIX, DCC} and then *) Select[ Range[2, 1000], StringLength@ SymbolName@ lst[[ # ]] == 3 &] (* _Robert G. Wilson v_, Aug 12 2008 *)
%Y A142958 Cf. A178968.
%K A142958 base,easy,nonn
%O A142958 1,1
%A A142958 David Bodycombe (davidbod(AT)hotmail.com), Jul 12 2008
%E A142958 More terms from _Robert G. Wilson v_, Aug 12 2008