\[\boxed{\mathbf{705\ (705).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[b_{n} = - n^{2} + 15n - 20\]
\[- n^{2} + 15n - 20 > 16\ \ \]
\[- n^{2} + 15n - 36 > 0\]
\[n^{2} - 15n + 36 < 0\]
\[n_{1} + n_{2} = 15,\ \ n_{1} = 12\]
\[n_{1}n_{2} = 36,\ \ n_{2} = 3\]
\[Тогда\ 4;5;6;7;8;9;10;\]
\[11 - 8\ членов.\]
\[Ответ:8.\]