login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Number of necklace compositions of n with distinct circular differences.
7

%I #6 May 11 2019 18:31:41

%S 1,1,2,3,5,4,10,16,23,34,53,66,113,164,262,380,567,821,1217,1778,2702,

%T 3919,5760,8520,12375

%N Number of necklace compositions of n with distinct circular differences.

%C 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.

%C The circular differences of a composition c of length k are c_{i + 1} - c_i for i < k and c_1 - c_i for i = k. For example, the circular differences of (1,2,1,3) are (1,-1,2,-2).

%H Gus Wiseman, <a href="/A325325/a325325.txt">Sequences counting and ranking integer partitions by the differences of their successive parts.</a>

%e The a(1) = 1 through a(8) = 16 necklace compositions:

%e (1) (2) (3) (4) (5) (6) (7) (8)

%e (12) (13) (14) (15) (16) (17)

%e (112) (23) (24) (25) (26)

%e (113) (114) (34) (35)

%e (122) (115) (116)

%e (124) (125)

%e (133) (134)

%e (142) (143)

%e (223) (152)

%e (1213) (224)

%e (233)

%e (1124)

%e (1142)

%e (1214)

%e (11213)

%e (11312)

%t neckQ[q_]:=Array[OrderedQ[{q,RotateRight[q,#]}]&,Length[q]-1,1,And];

%t Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],neckQ[#]&&UnsameQ@@Append[Differences[#],First[#]-Last[#]]&]],{n,15}]

%Y Cf. A000079, A000740, A008965, A034297, A059966, A070211, A318728, A318748, A320348, A325545, A325551, A325554, A325556.

%K nonn,more

%O 1,3

%A _Gus Wiseman_, May 10 2019