Answer:
A₍ₙ₎ = 23 - 2n
Step-by-step explanation:
A₍₁₎ = 23 - 2 x 1 = 21
A₍₂₎ = 23 - 2 x 2 = 19
A₍₃₎ = 23 - 2 x 3 = 17
