Computing cubes Establishing the invariant {0N} {(i | 0i<0 a[i] = i 3 ) 00N 0 = 0 3 1 = 3*0 2 + 3*0 + 1 6 = 6*0 + 6} k := 0; r := 0; s := 1; t := 6; {(i | 0i<k a[i] = i 3 ) 0kN r = k 3 s = 3*k 2 + 3*k + 1 t = 6*k + 6}
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