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A329362
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Length of the co-Lyndon factorization of the first n terms of A000002.
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9
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0, 1, 2, 3, 2, 2, 3, 2, 3, 4, 3, 4, 5, 4, 3, 4, 3, 3, 4, 5, 4, 5, 3, 3, 4, 3, 4, 5, 4, 3, 4, 3, 3, 4, 3, 4, 5, 4, 5, 6, 5, 4, 5, 4, 5, 6, 5, 6, 4, 4, 5, 4, 4, 5, 6, 5, 6, 7, 6, 5, 6, 5, 6, 7, 6, 7, 8, 7, 6, 7, 6, 5, 6, 5, 6, 7, 6, 7, 5, 5, 6, 7, 6, 7, 8, 7, 6, 7
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OFFSET
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0,3
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COMMENTS
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The co-Lyndon product of two or more finite sequences is defined to be the lexicographically minimal sequence obtainable by shuffling the sequences together. For example, the co-Lyndon product of (231) and (213) is (212313), the product of (221) and (213) is (212213), and the product of (122) and (2121) is (1212122). A co-Lyndon word is a finite sequence that is prime with respect to the co-Lyndon product. Equivalently, a co-Lyndon word is a finite sequence that is lexicographically strictly greater than all of its cyclic rotations. Every finite sequence has a unique (orderless) factorization into co-Lyndon words, and if these factors are arranged in a certain order, their concatenation is equal to their co-Lyndon product. For example, (1001) has sorted co-Lyndon factorization (1)(100).
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LINKS
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EXAMPLE
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The co-Lyndon factorizations of the initial terms of A000002:
() = 0
(1) = (1)
(12) = (1)(2)
(122) = (1)(2)(2)
(1221) = (1)(221)
(12211) = (1)(2211)
(122112) = (1)(2211)(2)
(1221121) = (1)(221121)
(12211212) = (1)(221121)(2)
(122112122) = (1)(221121)(2)(2)
(1221121221) = (1)(221121)(221)
(12211212212) = (1)(221121)(221)(2)
(122112122122) = (1)(221121)(221)(2)(2)
(1221121221221) = (1)(221121)(221)(221)
(12211212212211) = (1)(221121)(2212211)
(122112122122112) = (1)(221121)(2212211)(2)
(1221121221221121) = (1)(221121)(221221121)
(12211212212211211) = (1)(221121)(2212211211)
(122112122122112112) = (1)(221121)(2212211211)(2)
(1221121221221121122) = (1)(221121)(2212211211)(2)(2)
(12211212212211211221) = (1)(221121)(2212211211)(221)
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MATHEMATICA
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kolagrow[q_]:=If[Length[q]<2, Take[{1, 2}, Length[q]+1], Append[q, Switch[{q[[Length[Split[q]]]], q[[-2]], Last[q]}, {1, 1, 1}, 0, {1, 1, 2}, 1, {1, 2, 1}, 2, {1, 2, 2}, 0, {2, 1, 1}, 2, {2, 1, 2}, 2, {2, 2, 1}, 1, {2, 2, 2}, 1]]]
kol[n_Integer]:=If[n==0, {}, Nest[kolagrow, {1}, n-1]];
colynQ[q_]:=Array[Union[{RotateRight[q, #], q}]=={RotateRight[q, #], q}&, Length[q]-1, 1, And];
colynfac[q_]:=If[Length[q]==0, {}, Function[i, Prepend[colynfac[Drop[q, i]], Take[q, i]]]@Last[Select[Range[Length[q]], colynQ[Take[q, #]]&]]];
Table[Length[colynfac[kol[n]]], {n, 0, 100}]
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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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