\[ \boxed{ {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) =-{\frac { \left( -{a}^{2} \left( \sinh \left( x \right) \right) ^{2}-n \left( n-1 \right) \right) y \left( x \right) }{ \left( \sinh \left( x \right) \right) ^{2}}}=0} \]