Find the odd man out 864, 420, 200, 85, 40, 16, 6

Find the odd man out 864, 420, 200, 85, 40, 16, 6

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #3242