The value of
(1−ω+ω2)(1−ω2+ω4)(1−ω4+ω8)(1−ω8+ω16) is, where ω is the cube root of unity
(1−ω+ω2)(1−ω2+ω4)(1−ω4+ω8)(1−ω8+ω16)
[∵ω3=1]
=(1−ω+ω2)(1−ω2+ω)(1−ω+ω2)(1−ω2+ω)
Using 1+ω+ω2=0,
=(−ω−ω)(−ω2−ω2)(−ω−ω)(−ω2−ω2)
=(−2ω)(−2ω2)(−2ω)(−2ω2)
=16ω6=16 [∵ω3=1]