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All you need to know is that 
i2 = -1
(-1)EVEN = 1
(-1)ODD = -1
i32 = i2*16 = (i2)16 = (-1)16 = 1
Another example with an even power of i:
i58 = i2*29 = (i2)29 = (-1)29 = -1
Another example with an odd power of i:
i75 = i74+1 = i74i1 = i2*37i = (i2)37i = (-1)37i = -1i = -i
Another example with an odd power of i:
i201 = i200+1 = i200i1 = i2*100i = (i2)100i = (-1)100i = 1i = i
Edwin