3 |
12. x:{a...z-1}, y:{x+1...z}.
12. ( u:{a...x}. s(u,n) = p)
12. & s(x+1,n) p
12. & s(y-1,n) q
12. & ( u:{y...z}. s(u,n) = q)
x:{a...z-1}, y:{x+1...z}, p',q':Peg.
( u:{a...x}. s(u,n) = p) & ( u:{y...z}. s(u,n) = q)
& s(x) = ( i.p') {1...n-1} Peg & s(y) = ( i.q') {1...n-1} Peg
& p p'
& q q'
 | 20 steps |