OFFSET
1,2
COMMENTS
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.
EXAMPLE
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)
MATHEMATICA
aperQ[q_]:=Array[RotateRight[q, #1]&, Length[q], 1, UnsameQ];
Select[Range[100], aperQ[Last/@FactorInteger[#]]&]
CROSSREFS
Complement of A329140.
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.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 09 2019
STATUS
approved