Leonhard Euler (Image source) 
This program will allow you to obtain the numerical solution to the first order initial value problem:
using one of three different methods; Euler's method, Heun's method (also known as the improved Euler method), and a fourthorder RungeKutta method. To solve a problem, choose a method, fill in the fields below, choose the output format, and then click on the "Submit" button. A wide range of functions, e.g. exp(t) and sinh(t), are supported and whitespace is allowed. Mathematical expressions are entered just as they would be in most programming languages:
For example, the function (1+y^{2})e^{−t}sin(2t) could be entered in either of the following two ways:
