Answer:
To find the function rule for this sequence, we need to identify the pattern or rule that governs how each term is generated. In this case, it looks like the terms are alternating between multiplying by 2 and then subtracting 8.
a. Function Rule:
aₙ = a₁ * 2^(n-1) - 8
b. To find a₂₀ using this rule:
a₂₀ = a₁ * 2^(20-1) - 8
a₂₀ = 16 * 2^19 - 8
a₂₀ = 16 * 524288 - 8
a₂₀ = 8,388,544 - 8
a₂₀ = 8,388,536
So, a₂₀ is equal to 8,388,536.