Around a middle (0,0) that is a circle.
Cartesian for a circle =
x= a * cos(angle)
y= a * sin(angle)
a = radius
So, if you wanna place them on a circle around the middle(0,0), just add a certain degrees to angle each time an account is created, and you know x and y. How much you want to add depends on the needed space. Say the space needed is a circle with diameter b.
Then the first circle describing the first round around the middle must have at least radius a = b*6 (i think)
Now you add 360/ (round((pi*2*a) / b)) every time an account registers to angle.
When that circle is full, you add b to a.
And again you add 360/ (round((pi*2*b) / d)) every time an account registers, until again also that circle is full.
When that circle is full, you add b to a. ... and so on
But, that is kinda mimicking a spiral.
Cartesian for a simple spiral =
x= (a + (b*angle)) * (cos(angle))
y= (a + (b*angle)) * (sin(angle))
a kinda says where you start from the middle, while b controls the distance between successive turnings…
Now again, just add a value to angle, and you know x and y.
I just dont know how much degrees in this case. Guess you got to find that yourself or ask a smarter dude then me.