The full active table becomes easier when you look for the three rule-groups instead of memorizing 14 unrelated forms.
ExampleWhat happenedGroup
لَنْ يَفْعُلَfinal Dhammah became Fathah5 forms
لَنْ يَفْعُلَاNoon-e-I'raabi dropped7 forms
لَنْ يَفْعُلْنَno visible change2 forms
Use the rule first; memorization becomes easier afterward.