Problem Solving (PS) | Re: In a sequence for which an=a(n−1)+(−1)n(n)(k) for all values n>1 , wh

Hi,
I encountered this question and some similar questions on Veritas tests.
How to solve this question in less than 2 mins?
Unable to see a pattern until I solve till a6. During tests I had to take a wrong guess inorder to complete test in time, however during revisions I was able to solve it correctly in about 4 mins.
Its hard to complete tests in time with such question.

Please help with a relatively faster approach to such questions.

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