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A162761
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Suppose a lift can hold only C people, and N people are waiting at floors 1, 2, ..., N, while their destinations are floors N, N - 1, ..., 2, 1 respectively. When C = 1 and the lift starts at floor 1, what is the minimal stairs the lift must move before everyone get to their destinations?
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0
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0, 2, 4, 9, 13, 20, 26, 35, 43, 54, 64, 77, 89, 104, 118, 135, 151, 170, 188, 209, 229, 252, 274, 299, 323, 350, 376, 405, 433, 464, 494, 527
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| For n = 2 the a(2) = 2 means the lift needs move only 2 stairs to transport everyone to the destination: the lift loads person at floor 1, and moves to floor 2(1 stair), unloads and loads person at floor 2, then moves to floor 1(1 stair) and unloads.
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CROSSREFS
| Sequence in context: A129376 A024925 A162342 * A114885 A049793 A090942
Adjacent sequences: A162758 A162759 A162760 * A162762 A162763 A162764
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KEYWORD
| nonn
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AUTHOR
| Do Zerg (daidodo(AT)gmail.com), Jul 13 2009
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