MathCastle
Proof Writing & Problem SolvingSuperchallenge

Proof Writing & Problem Solving · Superchallenge problem

Let a1=a2=a3=1a_1 = a_2 = a_3 = 1 and, for n≥3n \ge 3, an+1=anan−1+2an−2a_{n+1} = \dfrac{a_n a_{n-1} + 2}{a_{n-2}}. Strong induction shows every term is an integer. What is a12a_{12}?

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