%I #2 Mar 30 2012 17:39:58
%S 1,2,3,4,10,5,8,7,32,13,34,15,6,12,9,48,21,11,16,14,17,42,19,170,20,
%T 43,64,46,65,47,68,58,69,59,80,62,81,63,18,255,22,51,25,60,26,192,37,
%U 195,38,204,41,207,85,35,341,40,23,128,29,130,31,136,53,138,55,160,61,162
%N a(n) is the smallest integer not yet in the sequence with no common base-4 digit with a(n-1).
%C Numbers of A031945 do not appear in this sequence.
%e The fifth term cannot be 5(base10)=11(base4), 6(base10)=12(base4), 7(base10)=13(base4), 8(base10)=20(base4) or 9(base10)=21(base4) because each of them has either a 0 or a 1 in its base-4 representation, which it would have in common with 4(base10)=10(base4). So a(5)=10(base10)=22(base4) which displays only digits of 2 in base 4.
%Y Cf. A067581 (base-10), A158928 (base-3), A158930 (base-5).
%K base,easy,nonn
%O 1,2
%A _R. J. Mathar_, Mar 31 2009