Though maybe we could have A3.1 Gen 2x2 for thick blue paper with glossy texture folded 4 times but 2 of those folds weren't down the middle.
It depends on your point of view on what you are comparing.
A0 area = 0.5^0 = 1 m^2 A1 area = 0.5^1 = 0.5 m^2 A2 area = 0.5^2 = 0.25 m^2 A3 area = 0.5^3 = 0.125 m^2
A1 area = 1 m^2 A2 area = 0.5 = 0.5 ^ (2-1) m^2 A3 area = 0.25 = 0.5 ^ (3-1) m^2
A0 = 1/(2^0) m^2
A1 = 1/(2^1) m^2
A2 = 1/(2^2) m^2
And so on
(EDIT for formatting and also to observe a sibling post to mine is making the same point)
Though maybe we could have A3.1 Gen 2x2 for thick blue paper with glossy texture folded 4 times but 2 of those folds weren't down the middle.