You might consider:
- A Programmer's Introduction to Mathematics (Kun) link
- One of these math courses/books: link
- Intro to Statistical Learning (James et al.) link
- Elements of Statistical Learning (Hasti et al.,) link
- A First Course in Linear Optimization link
- Intro to Applied Linear Algebra link
It may help if you can narrow down to a particular topic or area (e.g., you may be interested in mathematical optimization, stochastic processes, dynamical systems, simulation, statistical learning, networks). Here is a link to a nice compilation of different areas of math that may help you learn about some of the more theoretical areas: link. If you are specifically interested in the natural world, you may want to search for books that related to "computational ecology" or "computational biology."