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 A032240 Number of identity bracelets of n beads of 3 colors. 1
 3, 3, 1, 3, 12, 37, 117, 333, 975, 2712, 7689, 21414, 60228, 168597, 475024, 1338525, 3788400, 10741575, 30556305, 87109332, 248967446, 713025093, 2046325125, 5883406830, 16944975036, 48880411272, 141212376513 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n>2 also number of asymmetric bracelets with n beads of three colors. - Herbert Kociemba, Nov 29 2016 LINKS C. G. Bower, Transforms (2) F. Ruskey, Necklaces, Lyndon words, De Bruijn sequences, etc. [Cached copy, with permission, pdf format only] FORMULA "DHK" (bracelet, identity, unlabeled) transform of 3, 0, 0, 0... From Herbert Kociemba, Nov 29 2016: (Start) More generally, gf(k) is the g.f. for the number of asymmetric bracelets with n beads of k colors. gf(k): Sum_{n>=1} mu(n)*( -log(1-k*x^n)/n - Sum_{i=0..2} binomial(k,i)x^(n*i)/(1-k*x^(2*n)) )/2 (End) MATHEMATICA m = 3; (* asymmetric bracelets of n beads of m colors *) Table[Sum[MoebiusMu[d] (m^(n/d)/n - If[OddQ[n/d], m^((n/d + 1)/2), ((m + 1) m^(n/(2 d))/2)]), {d, Divisors[n]}]/2, {n, 3, 20}] (* Robert A. Russell, Mar 18 2013 *) mx=40; gf[x_, k_]:=Sum[MoebiusMu[n]*(-Log[1-k*x^n]/n-Sum[Binomial[k, i]x^(n i), {i, 0, 2}]/(1-k x^(2n)))/2, {n, mx}]; ReplacePart[Rest[CoefficientList[Series[gf[x, 3], {x, 0, mx}], x]], {1->3, 2->3}] (* Herbert Kociemba, Nov 29 2016 *) CROSSREFS Sequence in context: A261633 A277103 A120919 * A275625 A306148 A106836 Adjacent sequences:  A032237 A032238 A032239 * A032241 A032242 A032243 KEYWORD nonn AUTHOR STATUS approved

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Last modified January 16 03:30 EST 2019. Contains 319184 sequences. (Running on oeis4.)