Proof WritingHardInduction ShareInduction · Hard problemDefine a1=1a_1 = 1a1=1 and, for n≥2n \ge 2n≥2, an=a1+a2+⋯+an−1+1a_n = a_1 + a_2 + \cdots + a_{n-1} + 1an=a1+a2+⋯+an−1+1. Strong induction proves a closed form. What is a15a_{15}a15?Check Show answer Walk through it step by step Practice more like this Review this concept