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Forum## Problem of the Week 951## Upside Down LCD
In an LCD display some numbers, when viewed upside-down, are images of other numbers. For example, 1995 becomes 5661. The fifth number that can be read upside down is 8, and the 15th is 21, which is 12 when viewed upside-down. What is the millionth number that is meaningful upside-down? ------------- An LCD numeral is obtained by filling in some of the 7 lines in the figure below. -- | | -- | | -- 0: all but the central hyphen 1: The two right-hand verticals 8: All 2 -- 3 -- | | -- -- | | -- -- 4 5 -- | | | -- -- | | -- 6 -- 7 -- 9 -- | | | | -- -- | | | | -- -- © Copyright 2002 Stan Wagon. Reproduced with permission. |

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7 February 2002