|
| |
|
|
A072605
|
|
Number of necklaces of n beads and up to n unlabeled (interchangeable) colors.
|
|
3
|
|
|
|
1, 2, 4, 13, 50, 270, 1641, 11945, 96784, 887982, 8939051, 99298354, 1195617443, 15619182139, 219049941201, 3293800835940, 52746930894774, 897802366250126, 16167544246362567, 307372573011579188, 6148811682561390279
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
LINKS
|
Table of n, a(n) for n=1..21.
Frank Ruskey, Necklaces with Fixed Density
Eric Weisstein's world of Mathematics, Necklaces
|
|
|
FORMULA
|
See Mathematica line.
|
|
|
MATHEMATICA
|
Needs["DiscreteMath`Combinatorica`"]; neck[li:{__Integer}] := Module[{n, d}, n=Plus@@li; d=n-First[li]; Fold[ #1+(EulerPhi[ #2]*(n/#2)!)/Times@@((li/#2)!)&, 0, Divisors[GCD@@li]]/n]; Table[ Plus@@(neck /@ Partitions[n]), {n, 24}]
|
|
|
CROSSREFS
|
Cf. A052307.
Sequence in context: A005164 A058134 A069730 * A161905 A030953 A030811
Adjacent sequences: A072602 A072603 A072604 * A072606 A072607 A072608
|
|
|
KEYWORD
|
easy,nonn
|
|
|
AUTHOR
|
Wouter Meeussen, Aug 06 2002
|
|
|
STATUS
|
approved
|
| |
|
|
