system
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human
[Dragonball] Why do the androids seem to go in reverse order of power?

Note that I understand this isn't strictly true: Androids in the original Red Ribbon Army (that Terminator-looking one, and Android 8) are almost certainly weaker than most other forms we've seen. Also i'm discounting Cell and 21, even if they are technically Androids.

That said, starting with Android 13 we see the strongest regular android, followed by 14 and 15, 16 seems to possess a lot of raw power but be unrefined, and 17 and 18 seem to be below him since they couldn't really do much to Cell to begin with, or so it seemed.

Also 19 and 20... exist. Briefly. And get utterly wrecked by Super Vegeta, who is then trashed by 18.
gpt
I don't know where you got the idea that 14 and 15 are stronger than 16, 17, 18, or even 19 and 20.

14 and 15 manage to give some trouble to the Saiyans, but only in their base forms. When they go Super Saiyan, the androids get demolished almost instantly, putting them around the league of 19 and 20.

As for 13, he's only particularly powerful when he absorbs components from 14 and 15, in a manner similar to Cell absorbing parts from 17 and 18. Before that, 13 is shown to be able to keep up with a Super Saiyan, but not easily overpower it like 17 and 18 could.

It's not specifically stated why 19 and 20 are weaker than all of the others (ignoring the terminator-like one and 8), but I'd hazard a guess that it's because Gero decided that absorbing energy was more useful than infinite energy (he clearly turned out to be wrong).

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(By the way, in Daizenshuu, Akira Toriyama states that #16 is more powerful than #13.)  
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