The 'abundance' group
These nouns refer to a number, quantity, or amount. This use is productive with plural numbers, for example in threes.
in abundance in batches in bulk in dribs and drabs in droves in duplicate in flocks in groups (of ...) in ones and twos in packs of ... in pairs in plenty in profusion in quantity in sets of ... in ... numbers in ... quantities
The reason there are shortages is that water is not transferred from areas where it is available in abundance to those where it is needed.
Its members are leaving in droves.
Penguin chicks have been dying in large numbers in at least three widely separated parts of Antarctica.
Groups and pairs also have the pattern into N.
The children are split into groups of 16, each named after a fictional character such as Mickey Mouse.