# Think First!

Number Theory Level 3

Consider the sequence $$a_0,a_1,\ldots$$ where $$a_0=\frac{3}{11},$$ $$a_1 = -6,$$ and $$a_n= a_{n+1}+a_{n-1}$$ for $$n\ge 1.$$ Find the value of: $a_{23}+a_{24}+a_{25}+a_{26}+a_{27}+a_{28}.$

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