OFFSET
0,4
FORMULA
Moebius transform of A006840 (Christian Bower).
MATHEMATICA
b[n_] := (1/(2n)) DivisorSum[n, EulerPhi[n/#] Binomial[2# - 1, # - 1] + EulerPhi[2(n/#)] 2^(# - 1) &];
A006840[n_] := If[n == 0, 1, (b[n] + 2^(n - 2) + Binomial[n - Mod[n, 2], Quotient[n, 2]]/2)/2];
a[n_] := If[n == 0, 1, Sum[MoebiusMu[n/d] A006840[d], {d, Divisors[n]}]];
Array[a, 30, 0] (* Jean-François Alcover, Aug 28 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved