A019536 -id:A019536 - cp's OEIS frontend

A298971 Number of compositions of n that are proper powers of Lyndon words.

0, 1, 1, 2, 1, 4, 1, 5, 3, 8, 1, 16, 1, 20, 9, 35, 1, 69, 1, 110, 21, 188, 1, 381, 7, 632, 59, 1184, 1, 2300, 1, 4115, 189, 7712, 25, 14939, 1, 27596, 633, 52517, 1, 101050, 1, 190748, 2247, 364724, 1, 703331, 19, 1342283, 7713, 2581430, 1, 4985609, 193

Offset: 1

Gus Wiseman, Jan 30 2018

nonn

a(n) is the number of compositions of n that are not Lyndon words but are of the form p * p * ... * p where * is concatenation and p is a Lyndon word.

			The a(12) = 16 compositions: 111111111111, 1111211112, 11131113, 112112112, 11221122, 114114, 12121212, 123123, 131313, 132132, 1515, 222222, 2424, 3333, 444, 66.

Cf. A000005, A000031, A000740, A000961, A001045, A008965, A019536, A034691, A051953, A052823, A059966, A060223, A178472, A185700, A296302, A296373.

Table[Sum[DivisorSum[d,MoebiusMu[d/#]*(2^#-1)&]/d,{d,Most@Divisors[n]}],{n,100}]

a(n) = sumdiv(n, d, (2^d-1)*(eulerphi(n/d)-moebius(n/d))/n); \\ Michel Marcus, Jan 31 2018

a(n) = Sum_{d|n} (2^d-1)*(phi(n/d)-mu(n/d))/n.

a(n) = A008965(n) - A059966(n).

A318810 Number of necklace permutations of a multiset whose multiplicities are the prime indices of n > 1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 3, 1, 1, 2, 6, 1, 6, 1, 4, 3, 1, 1, 12, 4, 1, 16, 5, 1, 10, 1, 24, 3, 1, 5, 30, 1, 1, 4, 20, 1, 15, 1, 6, 30, 1, 1, 60, 10, 20, 4, 7, 1, 90, 7, 30, 5, 1, 1, 60, 1, 1, 54, 120, 10, 21, 1, 8, 5, 35, 1, 180, 1, 1, 70, 9, 14, 28, 1

Offset: 1

Gus Wiseman, Sep 04 2018

nonn

This multiset is generally not the same as the multiset of prime indices of n. For example, the prime indices of 12 are {1,1,2}, while a multiset whose multiplicities are {1,1,2} is {1,1,2,3}.
A necklace is a finite sequence that is minimal among its cyclic permutations.
a(1) = 1 by convention.

			The a(21) = 3 necklace permutations of {1,1,1,1,2,2} are: (111122), (111212), (112112). Only the first two are Lyndon words, the third being periodic.

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Cf. A000670, A008480, A019536, A056239, A060223, A112798, A298941, A305936, A318762, A318808, A318809.

nrmptn[n_]:=Join@@MapIndexed[Table[#2[[1]],{#1}]&,If[n==1,{},Flatten[Cases[FactorInteger[n]//Reverse,{p_,k_}:>Table[PrimePi[p],{k}]]]]];
neckQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And];
Table[Length[Select[Permutations[nrmptn[n]],neckQ]],{n,2,100}]

sig(n)={my(f=factor(n)); concat(vector(#f~, i, vector(f[i,2], j, primepi(f[i,1]))))}
count(sig)={my(n=vecsum(sig)); sumdiv(gcd(sig), d, eulerphi(d)*(n/d)!/prod(i=1, #sig, (sig[i]/d)!))/n}
a(n)={if(n==1, 1, count(sig(n)))} \\ Andrew Howroyd, Dec 08 2018

a(p) = 1 for prime p. - Andrew Howroyd, Dec 08 2018

a(1) inserted by Andrew Howroyd, Dec 08 2018

A334273 Numbers k such that the k-th composition in standard order is both a reversed necklace and a co-necklace.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 15, 16, 17, 18, 19, 21, 23, 31, 32, 33, 34, 35, 36, 37, 39, 42, 43, 45, 47, 63, 64, 65, 66, 67, 68, 69, 71, 73, 74, 75, 77, 79, 85, 87, 91, 95, 127, 128, 129, 130, 131, 132, 133, 135, 136, 137, 138, 139, 141, 143, 146, 147

Offset: 1

Gus Wiseman, Apr 25 2020

nonn

A necklace is a finite sequence of positive integers that is lexicographically less than or equal to any cyclic rotation. Co-necklaces are defined similarly, except with greater instead of less.

The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.

			The sequence of all reversed necklace co-necklaces begins:
    0: ()            31: (1,1,1,1,1)       69: (4,2,1)
    1: (1)           32: (6)               71: (4,1,1,1)
    2: (2)           33: (5,1)             73: (3,3,1)
    3: (1,1)         34: (4,2)             74: (3,2,2)
    4: (3)           35: (4,1,1)           75: (3,2,1,1)
    5: (2,1)         36: (3,3)             77: (3,1,2,1)
    7: (1,1,1)       37: (3,2,1)           79: (3,1,1,1,1)
    8: (4)           39: (3,1,1,1)         85: (2,2,2,1)
    9: (3,1)         42: (2,2,2)           87: (2,2,1,1,1)
   10: (2,2)         43: (2,2,1,1)         91: (2,1,2,1,1)
   11: (2,1,1)       45: (2,1,2,1)         95: (2,1,1,1,1,1)
   15: (1,1,1,1)     47: (2,1,1,1,1)      127: (1,1,1,1,1,1,1)
   16: (5)           63: (1,1,1,1,1,1)    128: (8)
   17: (4,1)         64: (7)              129: (7,1)
   18: (3,2)         65: (6,1)            130: (6,2)
   19: (3,1,1)       66: (5,2)            131: (6,1,1)
   21: (2,2,1)       67: (5,1,1)          132: (5,3)
   23: (2,1,1,1)     68: (4,3)            133: (5,2,1)

The aperiodic case is A334266.
Compositions of this type are counted by A334271.
Normal sequences of this type are counted by A334272.
Another ranking of the same compositions is A334274 (binary expansion).
Binary (or reversed binary) necklaces are counted by A000031.
Necklace compositions are counted by A008965.
All of the following pertain to compositions in standard order (A066099):
- Necklaces are A065609.
- Reversed necklaces are A333943.
- Co-necklaces are A333764.
- Reversed co-necklaces are A328595.
- Lyndon words are A275692.
- Co-Lyndon words are A326774.
- Reversed Lyndon words are A334265.
- Reversed co-Lyndon words are A328596.
- Aperiodic compositions are A328594.
Cf. A019536, A034691, A059966, A060223, A329138, A334269, A334270.

stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
neckQ[q_]:=Length[q]==0||Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And];
coneckQ[q_]:=Length[q]==0||Array[OrderedQ[{RotateRight[q,#],q}]&,Length[q]-1,1,And];
Select[Range[0,100],neckQ[Reverse[stc[#]]]&&coneckQ[stc[#]]&]

A334274 Numbers k such that the k-th composition in standard order is both a necklace and a reversed co-necklace.

Original entry on oeis.org

0, 1, 2, 3, 4, 6, 7, 8, 10, 12, 14, 15, 16, 20, 24, 26, 28, 30, 31, 32, 36, 40, 42, 48, 52, 54, 56, 58, 60, 62, 63, 64, 72, 80, 84, 96, 100, 104, 106, 108, 112, 116, 118, 120, 122, 124, 126, 127, 128, 136, 144, 160, 164, 168, 170, 192, 200, 204, 208, 212, 216

Offset: 1

Gus Wiseman, Apr 25 2020

nonn

Also numbers whose binary expansion is both a reversed necklace and a co-necklace.
A necklace is a finite sequence of positive integers that is lexicographically less than or equal to any cyclic rotation. Co-necklaces are defined similarly, except with greater instead of less.
The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.

			The sequence of all reversed co-necklace necklaces begins:
    0: ()            31: (1,1,1,1,1)      100: (1,3,3)
    1: (1)           32: (6)              104: (1,2,4)
    2: (2)           36: (3,3)            106: (1,2,2,2)
    3: (1,1)         40: (2,4)            108: (1,2,1,3)
    4: (3)           42: (2,2,2)          112: (1,1,5)
    6: (1,2)         48: (1,5)            116: (1,1,2,3)
    7: (1,1,1)       52: (1,2,3)          118: (1,1,2,1,2)
    8: (4)           54: (1,2,1,2)        120: (1,1,1,4)
   10: (2,2)         56: (1,1,4)          122: (1,1,1,2,2)
   12: (1,3)         58: (1,1,2,2)        124: (1,1,1,1,3)
   14: (1,1,2)       60: (1,1,1,3)        126: (1,1,1,1,1,2)
   15: (1,1,1,1)     62: (1,1,1,1,2)      127: (1,1,1,1,1,1,1)
   16: (5)           63: (1,1,1,1,1,1)    128: (8)
   20: (2,3)         64: (7)              136: (4,4)
   24: (1,4)         72: (3,4)            144: (3,5)
   26: (1,2,2)       80: (2,5)            160: (2,6)
   28: (1,1,3)       84: (2,2,3)          164: (2,3,3)
   30: (1,1,1,2)     96: (1,6)            168: (2,2,4)

The aperiodic case is A334267.
Compositions of this type are counted by A334271.
Normal sequences of this type are counted by A334272.
Binary (or reversed binary) necklaces are counted by A000031.
Necklace compositions are counted by A008965.
All of the following pertain to compositions in standard order (A066099):
- Necklaces are A065609.
- Reversed necklaces are A333943.
- Co-necklaces are A333764.
- Reversed co-necklaces are A328595.
- Lyndon words are A275692.
- Co-Lyndon words are A326774.
- Reversed Lyndon words are A334265.
- Reversed co-Lyndon words are A328596.
- Aperiodic compositions are A328594.
Cf. A019536, A034691, A059966, A060223, A329138, A334266, A334269, A334270.

stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
neckQ[q_]:=Length[q]==0||Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And];
coneckQ[q_]:=Length[q]==0||Array[OrderedQ[{RotateRight[q,#],q}]&,Length[q]-1,1,And];
Select[Range[0,100],neckQ[stc[#]]&&coneckQ[Reverse[stc[#]]]&]

A356954 Number of multisets of multisets, each covering an initial interval, whose multiset union is of size n and has weakly decreasing multiplicities.

Original entry on oeis.org

1, 1, 3, 6, 15, 30, 71, 145, 325, 680

Offset: 0

Gus Wiseman, Sep 09 2022

			The a(1) = 1 through a(4) = 15 multiset partitions:
  {{1}}  {{1,1}}    {{1,1,1}}      {{1,1,1,1}}
         {{1,2}}    {{1,1,2}}      {{1,1,1,2}}
         {{1},{1}}  {{1,2,3}}      {{1,1,2,2}}
                    {{1},{1,1}}    {{1,1,2,3}}
                    {{1},{1,2}}    {{1,2,3,4}}
                    {{1},{1},{1}}  {{1},{1,1,1}}
                                   {{1,1},{1,1}}
                                   {{1},{1,1,2}}
                                   {{1,1},{1,2}}
                                   {{1},{1,2,2}}
                                   {{1},{1,2,3}}
                                   {{1,2},{1,2}}
                                   {{1},{1},{1,1}}
                                   {{1},{1},{1,2}}
                                   {{1},{1},{1},{1}}

Gus Wiseman, Counting and ranking classes of multiset partitions related to gapless multisets

For unrestricted multiplicities we have A034691.
A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Other conditions: A035310, A063834, A330783, A356934, A356938, A356943.
Other types: A055932, A089259, A356945, A356955.
Cf. A055887, A072233, A270995, A304969, A349050, A349055, A356942.

sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
normQ[m_]:=Or[m=={},Union[m]==Range[Max[m]]];
strnorm[n_]:=Flatten[MapIndexed[Table[#2,{#1}]&,#]]&/@IntegerPartitions[n];
Table[Length[Select[Join@@mps/@strnorm[n],And@@normQ/@#&]],{n,0,5}]

A296976 List of normal Lyndon sequences ordered first by length and then reverse-lexicographically, where a finite sequence is normal if it spans an initial interval of positive integers.

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 1, 2, 3, 1, 2, 2, 1, 1, 2, 1, 4, 3, 2, 1, 4, 2, 3, 1, 3, 4, 2, 1, 3, 3, 2, 1, 3, 2, 4, 1, 3, 2, 3, 1, 3, 2, 2, 1, 2, 4, 3, 1, 2, 3, 4, 1, 2, 3, 3, 1, 2, 3, 2, 1, 2, 2, 3, 1, 2, 2, 2, 1, 2, 1, 3, 1, 1, 3, 2, 1, 1, 2, 3, 1, 1, 2, 2, 1, 1, 1, 2

Offset: 1

Gus Wiseman, Dec 22 2017

Row n is formed by A060223(n) sequences and has length A296975(n).

			Triangle of normal Lyndon sequences begins:
1,
12,
132,123,122,112,
1432,1423,1342,1332,1324,1323,1322,1243,1234,1233,1232,1223,1222,1213,1132,1123,1122,1112.

Cf. A000670, A019536, A060223, A095684, A185700, A281013, A294859, A296372, A296656, A296818, A296975-A296978.

LyndonQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And]&&Array[RotateRight[q,#]&,Length[q],1,UnsameQ];
normseqs[n_]:=Union@@Permutations/@Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1];
Table[Select[Reverse@normseqs@n,LyndonQ],{n,5}]

A318808 Number of Lyndon permutations of a multiset whose multiplicities are the prime indices of n > 1.

Original entry on oeis.org

1, 1, 0, 1, 0, 1, 0, 2, 1, 1, 0, 3, 0, 1, 2, 6, 0, 6, 0, 4, 2, 1, 0, 12, 3, 1, 14, 5, 0, 10, 0, 24, 3, 1, 5, 30, 0, 1, 3, 20, 0, 15, 0, 6, 30, 1, 0, 60, 8, 20, 4, 7, 0, 90, 7, 30, 4, 1, 0, 60, 0, 1, 51, 120, 9, 21, 0, 8, 5, 35, 0, 180, 0, 1, 70, 9, 14, 28, 0, 120

Offset: 1

Gus Wiseman, Sep 04 2018

nonn

This multiset is generally not the same as the multiset of prime indices of n. For example, the prime indices of 12 are {1,1,2}, while a multiset whose multiplicities are {1,1,2} is {1,1,2,3}.
The Lyndon product of two or more finite sequences is defined to be the lexicographically maximal sequence obtainable by shuffling the sequences together. For example, the Lyndon product of (231) with (213) is (232131), the product of (221) with (213) is (222131), and the product of (122) with (2121) is (2122121). A Lyndon word is a finite sequence that is prime with respect to the Lyndon product.
a(1) = 1 by convention.

			The a(30) = 10 Lyndon permutations of {1,1,1,2,2,3}:
  (111223)
  (111232)
  (111322)
  (112123)
  (112132)
  (112213)
  (112312)
  (113122)
  (113212)
  (121213)

Andrew Howroyd, Table of n, a(n) for n = 1..1000
Wikipedia, Lyndon word

Cf. A000670, A005651, A008480, A019536, A056239, A060223, A112798, A296372, A298941, A305936, A318762, A318810.

nrmptn[n_]:=Join@@MapIndexed[Table[#2[[1]],{#1}]&,If[n==1,{},Flatten[Cases[FactorInteger[n]//Reverse,{p_,k_}:>Table[PrimePi[p],{k}]]]]];
LyndonQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And]&&Array[RotateRight[q,#]&,Length[q],1,UnsameQ];
Table[Length[Select[Permutations[nrmptn[n]],LyndonQ]],{n,2,100}]

sig(n)={my(f=factor(n)); concat(vector(#f~, i, vector(f[i,2], j, primepi(f[i,1]))))}
count(sig)={my(n=vecsum(sig)); sumdiv(gcd(sig), d, moebius(d)*(n/d)!/prod(i=1, #sig, (sig[i]/d)!))/n}
a(n)={if(n==1, 1, count(sig(n)))} \\ Andrew Howroyd, Dec 08 2018

a(p) = 0 for prime p. - Andrew Howroyd, Dec 08 2018

A329145 Number of non-necklace compositions of n.

Original entry on oeis.org

0, 0, 1, 3, 9, 19, 45, 93, 197, 405, 837, 1697, 3465, 7011, 14193, 28653, 57825, 116471, 234549, 471801, 948697, 1906407, 3829581, 7689357, 15435033, 30973005, 62137797, 124630149, 249922665, 501078345, 1004468157, 2013263853, 4034666121, 8084640465

Offset: 1

Gus Wiseman, Nov 10 2019

nonn

A necklace composition of n is a finite sequence of positive integers summing to n that is lexicographically minimal among all of its cyclic rotations.

			The a(3) = 1 through a(6) = 19 compositions:
  (21)  (31)   (32)    (42)
        (121)  (41)    (51)
        (211)  (131)   (141)
               (212)   (213)
               (221)   (231)
               (311)   (312)
               (1121)  (321)
               (1211)  (411)
               (2111)  (1131)
                       (1221)
                       (1311)
                       (2112)
                       (2121)
                       (2211)
                       (3111)
                       (11121)
                       (11211)
                       (12111)
                       (21111)

Numbers whose prime signature is not a necklace are A329142.
Binary necklaces are A000031.
Necklace compositions are A008965.
Lyndon compositions are A059966.
Numbers whose reversed binary expansion is a necklace are A328595.
Cf. A000740, A001037, A019536, A070211, A178472, A318731, A329138, A329141.

neckQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And];
Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],!neckQ[#]&]],{n,10}]

a(n) = 2^(n-1) - A008965(n).

A019537 Number of special orbits for dihedral group of degree n.

Original entry on oeis.org

1, 2, 4, 14, 61, 414, 3416, 34274, 394009, 5113712, 73758368, 1170495180, 20263806277, 380048113202, 7676106638884, 166114210737254, 3834434327929981, 94042629562443206, 2442147034770292496, 66942194906543381336, 1931543452346146410965, 58519191359170883258606

Offset: 1

Manfred Goebel (goebel(AT)informatik.uni-tuebingen.de)

nonn

a(n) is the number of ways to color a necklace of n beads using at most n colors. Turning the necklace over does not count as different. - Robert A. Russell, May 31 2018

			For a(3) = 4, the necklaces are AAA, AAB, ABB, and ABC. Last one is chiral. For a(4) = 14, the necklacess are AAAA, AAAB, AABB, ABAB, ABBB, ABAC, ABCB, ACBC, AABC, ABBC, ABCC, ABCD, ABDC, and ACBD. Last six are chiral. - _Robert A. Russell_, May 31 2018

M. Goebel, On the number of special permutation-invariant orbits and terms, in Applicable Algebra in Engin., Comm. and Comp. (AAECC 8), Volume 8, Number 6, 1997, pp. 505-509 (Lect. Notes Comp. Sci.)

Cf. A019536.

Row sums of A273891.

Table[Sum[(k!/(2n)) DivisorSum[n, EulerPhi[#] StirlingS2[n/#,k] &] + (k!/4) (StirlingS2[Floor[(n+1)/2],k] + StirlingS2[Ceiling[(n+1)/2],k]), {k, 1, n}], {n, 1, 40}] (* Robert A. Russell, May 31 2018 *)

a(n) = sum(k=1, n, (k!/4)*(stirling(floor((n+1)/2),k,2) + stirling(ceil((n+1)/2),k,2)) + (k!/(2*n))*sumdiv(n, d, eulerphi(d)*stirling(n/d,k,2))); \\ Michel Marcus, Jun 06 2018

a(n) = Sum_{k=1..n} ((k!/4)*(S2(floor((n+1)/2),k) + S2(ceiling((n+1)/2),k)) + (k!/(2 n))*Sum_{d|n} phi(d)*S2(n/d,k)), where S2(n,k) is the Stirling subset number A008277. - Robert A. Russell, May 31 2018

a(n) ~ (n-1)! / (4 * log(2)^(n+1)). - Vaclav Kotesovec, Jul 21 2019

More terms (using A273891) from Alois P. Heinz, Jun 02 2016

A296977 List of normal Lyndon sequences ordered first by length and then lexicographically, where a finite sequence is normal if it spans an initial interval of positive integers.

Original entry on oeis.org

1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 3, 1, 3, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 3, 1, 1, 3, 2, 1, 2, 1, 3, 1, 2, 2, 2, 1, 2, 2, 3, 1, 2, 3, 2, 1, 2, 3, 3, 1, 2, 3, 4, 1, 2, 4, 3, 1, 3, 2, 2, 1, 3, 2, 3, 1, 3, 2, 4, 1, 3, 3, 2, 1, 3, 4, 2, 1, 4, 2, 3, 1, 4, 3, 2

Offset: 1

Gus Wiseman, Dec 22 2017

Row n is formed by A060223(n) sequences and has length A296975(n).

			Triangle of normal Lyndon sequences begins:
1,
12,
112,122,123,132,
1112,1122,1123,1132,1213,1222,1223,1232,1233,1234,1243,1322,1323,1324,1332,1342,1423,1432.

Cf. A000670, A019536, A060223, A095684, A185700, A281013, A294859, A296372, A296656, A296818, A296975, A296976.

LyndonQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And]&&Array[RotateRight[q,#]&,Length[q],1,UnsameQ];
normseqs[n_]:=Union@@Permutations/@Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1];
Table[Select[normseqs[n],LyndonQ],{n,5}]

cp's OEIS Frontend

A298971 Number of compositions of n that are proper powers of Lyndon words.

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A318810 Number of necklace permutations of a multiset whose multiplicities are the prime indices of n > 1.

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A334273 Numbers k such that the k-th composition in standard order is both a reversed necklace and a co-necklace.

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A334274 Numbers k such that the k-th composition in standard order is both a necklace and a reversed co-necklace.

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A356954 Number of multisets of multisets, each covering an initial interval, whose multiset union is of size n and has weakly decreasing multiplicities.

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A296976 List of normal Lyndon sequences ordered first by length and then reverse-lexicographically, where a finite sequence is normal if it spans an initial interval of positive integers.

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Mathematica

A318808 Number of Lyndon permutations of a multiset whose multiplicities are the prime indices of n > 1.

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PARI

Formula

A329145 Number of non-necklace compositions of n.

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