# Problem 13

Calculus Level 4

Let $${ a }_{ n }$$ be a sequence defined on positive integers as ${ a }_{ n }=\frac { 4n+\sqrt { { 4n }^{ 2 }-1 } }{ \sqrt { 2n+1 } +\sqrt { 2n-1 } }$ Find the value of $$\\ { a }_{ 1 }+{ a }_{ 2 }+........+{ a }_{ 60 }$$

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