Here are logos of Mathomatic, created on January 24, 2012. Copyright © 2012 George Gesslein II, but free to use for anything related to Mathomatic. Technically, they are licensed as Creative Commons Attribution-ShareAlike. Just mentioning Mathomatic is attribution enough.
Note that the SVG version does not display in most browsers. Some convenient, previously created sizes follow in PNG format:
|64×64 pixels||32×32 pixels|