Write down the next number in the series 1,11,21,1211,1231,131221,132231,232221 and call this number ABCDEF.
Assume N51 and W0 as usual and the cache is at
AB+C.(B+C+D) (B+C) (E+F)
AB+D.E (A+C+D+E+F) (C+E)
where AB means write the two numbers as one number, not multiply them.
