In article <3B223B7A.F6CF1B97@pobox.com>, Anton Sherwood says...

> I still can't see the rule!
> 
> The red squares along the axes fit the ordinary primes,
> but 2 and 5 are not prime in complex integers:
> 	(1+i)(1-i) = 2
> 	(2+i)(2-i) = 5

Oh no, it is nothing like this! In your way there is _no_ prime in 
complex numbers. What I did is simply as shown in the png...
I superimpose the Erathostenes-grids as shown for 2, 3, and 5.
These three result in the lower right image.

And so on for 7, 11, and as many as are required.

-- 
Regards,  Sander