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A257340
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Arrange numbers in a single clockwise spiral so that each number is relatively prime to its four (N,S,E,W) neighbors.
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24
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 12, 17, 15, 14, 19, 16, 23, 18, 25, 22, 21, 20, 27, 26, 29, 24, 31, 35, 32, 37, 28, 41, 33, 34, 39, 40, 43, 30, 47, 36, 49, 38, 45, 44, 51, 46, 53, 42, 55, 48, 59, 50, 57, 61, 52, 63, 58, 65, 54, 67, 69, 56, 71, 62, 73
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Start with 1; always choose smallest number which has not yet appeared.
It is conjectured that every number appears.
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LINKS
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EXAMPLE
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. | -4 | -3 | -2 | -1 | 0 | +1 | +2 | +3 | +4 | +5
. ---+--------+----+----+----+----+----+----+----+----+----
. |
. | +------------------------------------------------
. +4 | | 83 68 75 74 81 70 87 76 85 ...
. ---+ | +---------------------------------------+
. +3 | | 66 | 49 38 45 44 51 46 53 42 |
. ---+ | | +-----------------------------+ |
. +2 | | 79 | 36 | 25 22 21 20 27 26 | 55 |
. ---+ | | | +-------------------+ | |
. +1 | | 64 | 47 | 18 | 7 8 9 10 | 29 | 48 |
. ---+ | | | | +---------+ | | |
. 0 | | 77 | 30 | 23 | 6 | 1 2 | 11 | 24 | 59 |
. ---+ | | | | +----o | | | |
. -1 | | 60 | 43 | 16 | 5 4 3 | 13 | 31 | 50 |
. ---+ | | | +--------------+ | | |
. -2 | | 73 | 40 | 19 14 15 17 12 | 35 | 57 |
. ---+ | | +------------------------+ | |
. -3 | | 62 | 39 34 33 41 28 37 32 | 61 |
. ---+ | +----------------------------------+ |
. -4 | | 71 56 69 67 54 65 58 63 52 |
. ---+ +--------------------------------------------+
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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