What could be the maximum value?

${ a }_{ 1 },{ a }_{ 2 },{ a }_{ 3 },...{ a }_{ n }$ are positive integers such that ${ a }_{ 1 }<{ a }_{ 2 }<{ a }_{ 3 }...<{ a }_{ n }$

And,

$\dfrac { 1 }{ { a }_{ 1 } } +\dfrac { 1 }{ { a }_{ 2 } } +\dfrac { 1 }{ { a }_{ 3 } } +...+\dfrac { 1 }{ { a }_{ n } } =1$

Find maximum value for ${ a }_{ n}+1$ for $n=6$