Sequence: 1 / 2, - 1 / 6,1 / 12, - 1 / 20,1 / 30 What is the general formula of?

Sequence: 1 / 2, - 1 / 6,1 / 12, - 1 / 20,1 / 30 What is the general formula of?


Sequence: 1 / 2, - 1 / 6,1 / 12, - 1 / 20,1 / 30 The general formula of is
an = (-1)^(n+1) / [n(n+1)]



The first few terms of the sequence are - 2,6, - 12,20, - 30, so the general term formula of the sequence can be obtained


First, sign alternately to determine [(- 1) ^ n]
Observation, 2 = 1 * 2, 6 = 2 * 3, 12 = 3 * 4, 20 = 4 * 5, 30 = 5 * 6, so there is n (n + 1) term
comprehensive
an=[(-1)^n ]* n(n+1)

Elden Ring Premiere

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