OFFSET
1,1
COMMENTS
First differs from A304678 in having 1350 = 2^1 * 3^3 * 5^2. First differs from A316529 in having 150 = 2^1 * 3^1 * 5^2.
A number's prime signature (A124010) is the sequence of positive exponents in its prime factorization.
A necklace is a finite sequence that is lexicographically minimal among all of its cyclic rotations.
EXAMPLE
The sequence of terms together with their prime signatures begins:
2: (1)
3: (1)
4: (2)
5: (1)
6: (1,1)
7: (1)
8: (3)
9: (2)
10: (1,1)
11: (1)
13: (1)
14: (1,1)
15: (1,1)
16: (4)
17: (1)
18: (1,2)
19: (1)
21: (1,1)
22: (1,1)
MATHEMATICA
neckQ[q_]:=Array[OrderedQ[{q, RotateRight[q, #]}]&, Length[q]-1, 1, And];
Select[Range[2, 100], neckQ[Last/@FactorInteger[#]]&]
CROSSREFS
Complement of A329142.
Binary necklaces are A000031.
Necklace compositions are A008965.
Numbers whose reversed binary expansion is a necklace are A328595.
Numbers whose prime signature is a Lyndon word are A329131.
Numbers whose prime signature is aperiodic are A329139.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 09 2019
STATUS
approved