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 A061819 #7 Feb 13 2017 02:03:54 %S A061819 0,3,12,21,30,33,102,111,120,123,132,201,210,213,222,231,300,303,312, %T A061819 321,330,333,1002,1011,1020,1023,1032,1101,1110,1113,1122,1131,1200, %U A061819 1203,1212,1221,1230,1233,1302,1311,1320,1323,1332,2001,2010,2013,2022,2031 %N A061819 Multiples of 3 containing only digits 0,1,2,3. %H A061819 Harvey P. Dale, <a href="/A061819/b061819.txt">Table of n, a(n) for n = 1..1000</a> %H A061819 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>. %F A061819 a(n) = A007090(3n), i.e. can also be read as multiples of 3 (A008585) written in base 4. %e A061819 132 is a term containing digits less than 4. %t A061819 Select[3*Range[0,750],Max[IntegerDigits[#]]<4&] (* _Harvey P. Dale_, Jul 10 2014 *) %Y A061819 Cf. A061818. %K A061819 nonn,base,easy %O A061819 1,2 %A A061819 _Amarnath Murthy_, May 28 2001 %E A061819 Corrected and extended by Larry Reeves (larryr(AT)acm.org) and _Henry Bottomley_, May 30 2001