y_{1} = y_{i} + k_{1} (\frac{1}{2} dt)

y_{2} = y_{i} + k_{2} (\frac{1}{2} dt)

y_{3} = y_{i} + k_{3} dt

y_{i+1} = y_{i} + \frac{1}{6}(k_{1} + 2k_{2} + 2k_{3} + k_{4}) dt