Homepage of P. Christopher Staecker: Factor stencils

This is a set of factor stencils, designed by D.N. Lehmer.

To factor a large number, you use a formula which tells you which stencils to gather and line up together. The holes that go all the way through indicate the prime factors of your number.

About the factor stencils

Here's a short video I made about the factor stencils.

This is part of my series of videos about antique computing devices. Here is the full series playlist

More details

In the video I skipped over some details. This little PDF explains everything.

• Using Lehmer's factor stencils (PDF)

Download printables

Here is a PDF of the stencils for R values -50 to 50 which are meant to be printed on 8½ x 11 paper and punched with a standard 6mm or 1/4 inch hole punch.

• Factor stencils (PDF)
• Factor stencils SVG zip file of SVGs of stencils, 4 stencils per file
• Unlabeled factor stencils SVG zip file SVGs of unlabeled stencils that I used in the Cricut machine

All these images were generated by python code here:

• stencils.py

Other stuff

• Other pages about antique calculating devices