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 A219115 #7 May 07 2015 16:37:50 %S A219115 4,5,7,8,10,12,13,14,15,17,20,21,22,23,24,25,26,28,30,31,32,34,35,36, %T A219115 37,38,39,40,41,42,43,44,45,46,47,49,50,51,52,53,56,58,59,60,61,62,63, %U A219115 64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,82,84 %N A219115 Numbers whose squares have at least one 1 and one 2 in ternary representation. %C A219115 So a(n)^2 belongs to A125293. %C A219115 Complement of A176189. %H A219115 K. Mahler, <a href="http://matwbn.icm.edu.pl/ksiazki/aa/aa53/aa5316.pdf">The representation of squares to the base 3</a>, Acta Arith. Vol. 53, Issue 1 (1989), p. 99-106. %t A219115 Select[Range[100],DigitCount[#^2,3,1]>0&&DigitCount[#^2,3,2]>0&] (* _Harvey P. Dale_, May 07 2015 *) %Y A219115 Cf. A125293, A176189. %K A219115 nonn,base %O A219115 1,1 %A A219115 _Michel Marcus_, Nov 12 2012