Tính B = \(\frac{1}{7} + \frac{1}{91} + \frac{1}{247} + \frac{1}{475} + \frac{1}{775} + \frac{1}{1147}\)

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B = \(\frac{1}{7} + \frac{1}{91} + \frac{1}{247} + \frac{1}{475} + \frac{1}{775} + \frac{1}{1147}\)