The program decay.exe writes to a file in the same directory in this format

Lambda,0.027725
0,1760
1,1713
2,1655
3,1620
4,1576
5,1536
6,1483
7,1437
8,1402
9,1369


In general:
time,remaining nuclei

I have the kids import this into excel, and make a graph from there.