Here are a few of the ideas that we have done in the past.
#1 - We did sink or float with candy corn - then we let it sit for awhile to see what would happen.
#2 - I have 3 different size and colors of triangles. We patterned with them (I had more cut out than you see pictured). Then after we patterned, we stacked them by size shown and made a candy corn.
#3 - In each muffin cup I had an orange circle with a number on it. He then counted out how many candy corns belonged in each cup.
Here is a cute craft they enjoyed too. Ripping construction paper (or you can use scissors for cutting skill).