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A120061
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Number of universal cycles for permutations of n objects.
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1
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OFFSET
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2,2
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COMMENTS
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A universal cycle of permutations is a cycle of n! digits such that each permutation of {1,...,n} occurs exactly once as a block of n-1 consecutive digits (with its redundant final element suppressed). a(4)=2^7*3, a(5)=2^33*3^8*5^3, a(6)=2^190*3^49*5^33, a(7)=2^1217*3^123*5^119*7^5*11^28*43^35*73^20*79^21*109^35 ~=1.582284037*10^747.
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REFERENCES
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D. E. Knuth, The Art of Computer Programming, Volume 4, Fascicle 2, Generating All Tuples and Permutations. Ch. 7.2.1.2, Exercises 111 and 112, Page 75 and Answer to Exercise 112, pages 120-121.
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LINKS
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EXAMPLE
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(121323) is a universal cycle of permutations for n=3,
(123124132134214324314234) is one for n=4.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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