Find out the wrong number in the given sequence of numbers

Find out the wrong number in the given sequence of numbers. 1, 2, 6, 15, 31, 56, 91

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

~8 minAnswer checked instantly

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #10252

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