My teacher gave us a pyramid pattern to solve the coefficients of large exponents and then a pattern for the rest of the letters and their exponents but I can't for the life of me understand/remember what he said. I am specifically stuck on (a+b)^4.

Pyramid:

............1

..........1...1

........1...2...1

......1...3...3...1

....1...4...6...4...1

1...5...10...10...5...1