Henry Langner

```DPRKN6``` was used by default here, however it is designed for 2nd order ODEs which are not dependent on the first derivative. This could have lead to the wrong results....

> Try flipping a few signs. I have seen more than a few papers forget a `-` on one of the `a` values. Good idea, I will try that.

For the testing I used the ```Nystrom4``` solver which allows a dependence on the first derivative. The code is attached. The following table lists the difference between the numeric solution...