Necklaces vs Bracelets

Meeussen Wouter (bkarnd) wouter.meeussen at vandemoortele.com
Mon Aug 5 20:17:21 CEST 2002


ID Number: A047996
Sequence:  1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,2,2,1,1,1,1,3,4,3,1,1,1,1,
Name:      Triangle of circular binomial coefficients T(n,k), 0<=k<=n.
Comments:  T(n,k)=number of necklaces with k black beads, n-k white beads.
Formula : (1/n) * Sum_{d | (n,k)} phi(d)*binomial(n/d,k/d).



ID Number: A052307	
Sequence:  1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,2,2,1,1,1,1,3,3,3,1,1,1,1,	
           3,4,4,3,1,1,1,1,4,5,8,5,4,1,1,1,1,4,7,10,10,7,4,1,1,1,1,5,8,	
           16,16,16,8,5,1,1,1,1,5,10,20,26,26,20,10,5,1,1,1,1,6,12,29,	
           38,50,38,29,12,6,1,1,1,1,6	
Name:      Triangle: T(n,k): bracelets (reversible necklaces) with n black

              beads and n-k white beads.	
Formula : nihil !
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Author(s): Christian G. Bower (bowerc at usa.net), Nov 1999.

for even rows (=2n beads) and m=1..n this appears to be :
(1/2)*(C(2*(n\2),m\2) +Sum (d|(2n,m) phi(d)C(2n/d,m/d) ) - (-1)^n
if(even(n+m) ,0, C(n-1, floor(m/2-1/2) )	

who can give the formula for the complete A052307 ?

greets,

W.

Wouter Meeussen
email : wouter.meeussen at vandemoortele.com



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