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The Original London Sightseeing Tour-Hop On Hop Off     “When a man is tired of London, he is tired of life, for there is in London all that life can afford. ——Dr Samuel Johnson 1709-1784.” Duration: 24 hours pass Welcome to London and welcome to The Original Tour. Providing more than just a great way to travel around the capital, founded nearly 60 years ago at the time of The Festival of Britain, The Original Tour is now the largest and most popular sightseeing operator in the world. The Original Tour has become set up as the basic introduction to London. You are invited to experie对于正项数列，定义，若则数列的通项公式为       。