Range 1,2,2,1,2,2
Ran#→A:Ran#→B
5000→K
Lbl 1:Int(3Ran#)→N
N=1⇒Goto 2
N=2⇒Goto 3
.5A→A:.5B→B:Goto 4
Lbl 2:.5(.5+A)→A:.5(1+B)→B:Goto 4
Lbl 3:.5(1+A)→A:.5B→B
Lbl 4:A+1→X:B+1→Y:Plot X,Y
Dsz K:Goto 1
Plot X,Y:Line
I don't think Ran# gives a very even distribution. Ah well!