If Sn is the sum of the first n terms of a…

If Sn is the sum of the first n terms of a certain sequence and if Sn = n(n+3) for all positive integers n, what is the third term of the sequence?

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 #8811