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A208667
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Number of 2n-bead necklaces labeled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1.
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1
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3, 5, 8, 14, 24, 47, 89, 187, 396, 881, 1990, 4645, 10935, 26211, 63320, 154378, 378444, 933023, 2308957, 5735372, 14286908, 35683815, 89324138, 224057919, 563033979, 1417210457, 3572641304, 9018885122, 22796905056, 57692673963, 146167385345, 370710166435
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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All solutions for n=4:
..1....2....2....2....1....1....1....1....1....3....1....1....2....2
..2....3....3....3....2....2....2....2....2....4....2....2....3....3
..1....2....2....2....1....1....3....3....3....3....3....1....4....4
..2....3....3....3....2....2....4....2....2....4....2....2....3....3
..1....4....2....2....3....1....3....1....3....3....3....3....2....4
..2....3....3....3....4....2....4....2....4....4....2....2....3....3
..1....4....2....4....3....3....3....3....3....3....3....3....4....4
..2....3....3....3....2....2....2....2....2....4....2....2....3....3
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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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