%I #6 Aug 02 2016 10:25:22
%S 1,0,0,0,0,1,2,3,2,3,3,4,4,5,5,4,5,4,3,2,2,1,1,0,0,0,1,1,0,0,0,0,0,0,
%T 0,0,1,1,0,0,0,0,0,0,0,0,1,2,2,3,2,2,3,3,3,4,4,4,5,5,6,7,8,9,10,9,10,
%U 11,11,12,13,13,14,15,15,14,15,16,15,16,15,14
%N a(n)=(# 1's)-(# 2's) in first n terms of A031235.
%t Accumulate[Which[#==1,1,#==2,-1,True,0]&/@(Reverse[IntegerDigits[ #,5]]&/@ Range[ 0,40]//Flatten)] (* _Harvey P. Dale_, Aug 02 2016 *)
%K nonn
%O 1,7
%A _Clark Kimberling_