Problem Statement

The sequence is generated by following this pseudo-code:

Using A: Using B: Using C: Using B: Using C: (zero last occurred two steps back - before the one) Using B: Using C: (two last occurred two steps back - before the zero) Using C: (two last occurred one step back) Using C: (one last appeared six steps back) ...

Let's start with the solution:

1000 :1)=0
1010 I=1
1020 J=I-1
1030 #=J=0*1090
1040 #=:J)=:I)*1070
1050 J=J-1
1060 #=1030
1070 :I+1)=I-J
1080 #=1100
1090 :I+1)=0
1100 I=I+1
1110 #=I<1000*1020
1120 I=1
1130 #=1170
1140 I=991
1150 #=1170
1160 #=9999
1170 R=!
1180 N=10
1190 ?=:I)
1200 $=32
1210 I=I+1
1220 N=N-1
1230 #=N=0=0*1190
1240 ?=""
1250 #=R