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A329139
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Numbers whose prime signature is an aperiodic word.
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20
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1, 2, 3, 4, 5, 7, 8, 9, 11, 12, 13, 16, 17, 18, 19, 20, 23, 24, 25, 27, 28, 29, 31, 32, 37, 40, 41, 43, 44, 45, 47, 48, 49, 50, 52, 53, 54, 56, 59, 60, 61, 63, 64, 67, 68, 71, 72, 73, 75, 76, 79, 80, 81, 83, 84, 88, 89, 90, 92, 96, 97, 98, 99, 101, 103, 104
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listen;
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OFFSET
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1,2
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COMMENTS
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First differs from A319161 in having 1260 = 2*2 * 3^2 * 5^1 * 7^1. First differs from A325370 in having 420 = 2^2 * 3^1 * 5^1 * 7^1.
A number's prime signature (A124010) is the sequence of positive exponents in its prime factorization.
A sequence is aperiodic if its cyclic rotations are all different.
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LINKS
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EXAMPLE
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The sequence of terms together with their prime signatures begins:
1: ()
2: (1)
3: (1)
4: (2)
5: (1)
7: (1)
8: (3)
9: (2)
11: (1)
12: (2,1)
13: (1)
16: (4)
17: (1)
18: (1,2)
19: (1)
20: (2,1)
23: (1)
24: (3,1)
25: (2)
27: (3)
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MATHEMATICA
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aperQ[q_]:=Array[RotateRight[q, #1]&, Length[q], 1, UnsameQ];
Select[Range[100], aperQ[Last/@FactorInteger[#]]&]
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CROSSREFS
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Aperiodic compositions are A000740.
Aperiodic binary words are A027375.
Numbers whose binary expansion is aperiodic are A328594.
Numbers whose prime signature is a Lyndon word are A329131.
Numbers whose prime signature is a necklace are A329138.
Cf. A025487, A097318, A112798, A124010, A178472, A181819, A304678, A329133, A329135, A329136, A329137, A329142.
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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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