If the hedgehogs would be able to reproduce by simple division and could do it once a day…
Today – 1 hedgehog
Tomorrow – 2 hedgehogs
The day after tomorrow – 4 hedgehogs
On a 4th day – 8 hedgehogs
On a 5th day – 16 hedgehogs
On a 6th day – 32 hedgehogs
On a 7th day – 64 hedgehogs
On a [...]