A puzzle

[Armitage]

aefhiklmntvwxyz

bcdgjopqrsu

Tell me the rule/pattern/series/equation that is used to seperate the alphabet into these 2 groups.
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(anti-spoiler lines)
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[kranky]

I've seen this one before, but I'll play it straight and not post the answer yet.

 

[Armitage]

No Takers?
<bump>

 

[Basilisk6]

If this is what I think it is, you messed it up. The groups are:

AEFHIKLMNTVWXYZ and BCDGJOPQRSU

 

[Whitecloak]

curves?