The value of (7C0+7C1)+(7C1+7C2)+...+(7C6+7C7)
28−2
(7C0+7C1)+(7C1+7C2)+(7C2+7C3)+(7C3+7C4)+(7C4+7C5)+(7C5+7C6)+(7C6+7C7)
=1+2×7C1+2×7C2×7C3+2×7C4+2×7C5+2×7C6+1
=1+2×7C1+2×7C2×7C3+2×7C3+2×7C2+2×7C6+1
=2+22(7C1+7C2+7C3)
=2+22(7+72×6+73×62×5)
=2+252=254
=28−2