OFFSET
0,3
FORMULA
G.f.: k=3, Sum_{i>=1} (mu(i) - phi(i))*log(1 - k*x^i)/i.
EXAMPLE
Example: The 6 periodic necklaces with 4 beads and the colors A, B and C are AAAA, BBBB, CCCC, ABAB, ACAC and BCBC.
MATHEMATICA
mx=40; f[x_, k_]:=Sum[(MoebiusMu[i]-EulerPhi[i])Log[1-k*x^i]/i, {i, 1, mx}]; CoefficientList[Series[f[x, 3], {x, 0, mx}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Herbert Kociemba, Nov 25 2016
STATUS
approved