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A064280
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Number of distinct solutions to the order n checkerboard problem, symmetrical solutions excluded: place n pieces on an n X n board so there is exactly one piece in each row, column and main diagonal.
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1
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OFFSET
| 1,5
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REFERENCES
| Geoffrey Chase, Creative Computing 6(1), Jan 1980, 122.
Bahairiv Joshi, Unique Solutions to the Checkerboard Problem, Creative Computing 6(10), Oct 1980, 124-125.
Abijah Reed, Creative Computing 6(5), May 1980, 94.
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EXAMPLE
| The 4 X 4 solution is unique, excluding symmetrical solutions, with pieces at (1,1), (2,3), (3,4) and (4,2).
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CROSSREFS
| A007016 gives the number of solutions including symmetrical ones.
Cf. A007016.
Sequence in context: A205337 A081214 A194004 * A203379 A096424 A009629
Adjacent sequences: A064277 A064278 A064279 * A064281 A064282 A064283
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KEYWORD
| more,nonn
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AUTHOR
| Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu), Sep 24 2001
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