There's a lot of interesting number logic to be find. Try finding proof for your findings, or even go over to another numerical base to find "patterns" if you like.

Try this: Why does the last number of many arithmetic integer multiples (ab^n) have a period of no greater than 4? (E.g. 7*13=91, 7*13^2=1183, 7*13^3=15379 7*13^4=199927, 7*13^5=2599051, 7*13^6=33787663, 7*13^7=439239619, 7*13^8=5710115047, 7*13^9=74231495611...)

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram