Advice on Mathematica Writing by Keith Conrad
Examples of proofs by induction by K. Conrad
Combinatorics Through Guided Discovery Free Textbook by Kenneth P. Bogart: PDF
A simple visual editor for writing diagrams and converting it to Tikz github.com/yishn/tikzcd-editor, try it out at https://tikzcd.yichuanshen.de
Math students, connect with prospective employers here: MAA Career Resource Center
Use CamScanner app or another scan app to turn your hand-written work into PDF.