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177 problems, every one written from scratch, every wrong answer carrying the mistake that produces it. 708 explanations in all.

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NUMNumber & Arithmetic
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KA-0171
3 points, difficulty 1 of 3Level 11–12not yet calibrated
A sequence is defined by a(1) = 2 and a(n+1) = 2 a(n) - 1 for every n. What is a(6)?
PAT-05Recursive rulesalso CFT-03, PAT-07

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