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A343467 a(n) = -(1/n) * Sum_{d|n} phi(n/d) * (-5)^d. 2
5, -10, 45, -160, 629, -2590, 11165, -48910, 217045, -976258, 4438925, -20346440, 93900245, -435959830, 2034505661, -9536767660, 44878791365, -211927519090, 1003867701485, -4768372070128, 22706531350485, -108372079190350, 518301258916445, -2483526875847690, 11920928955078629 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
G.f.: Sum_{k>=1} phi(k) * log(1 + 5*x^k) / k.
a(n) = -(1/n) * Sum_{k=1..n} (-5)^gcd(n,k).
Product_{n>=1} 1 / (1 - x^n)^a(n) = g.f. for A261569.
MATHEMATICA
Table[-(1/n) Sum[EulerPhi[n/d] (-5)^d, {d, Divisors[n]}], {n, 1, 25}]
nmax = 25; CoefficientList[Series[Sum[EulerPhi[k] Log[1 + 5 x^k]/k, {k, 1, nmax}], {x, 0, nmax}], x] // Rest
CROSSREFS
Sequence in context: A328605 A122173 A083515 * A103971 A270085 A035406
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Apr 16 2021
STATUS
approved

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Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)