I'm trying to figure out a way to generate endless waves of enemies in a space shooter. The waves will progress after you kill each enemy in the current wave. I want a way to generate different types of enemies with different strengths. I've already set up all of these enemies, I just need numbers now.

I've been thinking you could use prime numbers and the distance between each prime number would be the number of enemies. The problem with this is that you wouldn't really have much of a difference in waves.

My next thought was to use the fibonacci sequence, but I'm still stuck.

Does anyone have any ideas on how accomplishing this?

I want waves to be something like this -

Wave 1

Tier1: 4

Tier2: 2

Tier3: 0

Tier4: 0

Tier5: 0

each tier is a type of enemy varying in health, speed and strength. So wave 1 would have a total of 6 enemies.