(# 1's)-(# 2's) in first n terms of A030413.

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =2a(5) =1a(6) =1a(7) =1a(8) =2a(9) =3a(10) =4a(11) =5a(12) =4a(13) =4a(14) =3a(15) =3a(16) =4a(17) =4a(18) =5a(19) =6a(20) =5a(21) =6a(22) =5a(23) =6a(24) =6a(25) =6a(26) =6a(27) =5a(28) =4a(29) =5