This is LaTeX code:
[latex]
+ qp^2 \left( {1 - p} \right)\left( {\left( {f_1 \left( {n_1 } \right)f_1 \left( {n_2 } \right) + f_1 \left( {n_1 } \right)f_1 \left( {n_3 } \right) + f_1 \left( {n_2 } \right)f_1 \left( {n_3 } \right)} \right)} \right) +
[/latex]