A382998 a(n) = Sum_{d|n} phi(n/d) * (-n)^(d-1).
1, -1, 11, -66, 629, -7750, 117655, -2097676, 43046889, -999990036, 25937424611, -743008622708, 23298085122493, -793714765724686, 29192926025492783, -1152921504875290680, 48661191875666868497, -2185911559727680349982, 104127350297911241532859
Offset: 1
Keywords
Programs
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PARI
a(n) = sumdiv(n, d, eulerphi(n/d)*(-n)^(d-1));
Formula
a(n) = (1/n) * A382997(n).
a(n) = Sum_{k=1..n} (-n)^(gcd(n,k) - 1).
a(n) = [x^n] Sum_{k>=1} phi(k) * log(1 + n*x^k) / k.
a(n) = [x^n] Sum_{k>=1} phi(k) * x^k / (1 + n*x^k).