For those unaware, patrols spawn on a timer, and the amount of patrols that spawn on that timer is based on a few factors, one of which being the number of groups (or formations, as I've been referring to them) of Helldivers active on the map. These formations are defined by any groups of players that are within 75m of another player. You don't have to all be within the same 75m radius, but as long as there's fewer than 75m between any two players, they're considered one formation.
There's a LOT more detail in this video: https://www.youtube.com/watch?v=Zp8xuf_dLDw