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Fungrim entry: aaef97

k=1ngcd ⁣(n,k)=dndφ ⁣(nd)\sum_{k=1}^{n} \gcd\!\left(n, k\right) = \sum_{d \mid n} d \varphi\!\left(\frac{n}{d}\right)
Assumptions:nZ0n \in \mathbb{Z}_{\ge 0}
\sum_{k=1}^{n} \gcd\!\left(n, k\right) = \sum_{d \mid n} d \varphi\!\left(\frac{n}{d}\right)

n \in \mathbb{Z}_{\ge 0}
Fungrim symbol Notation Short description
Sumnf(n)\sum_{n} f(n) Sum
GCDgcd ⁣(a,b)\gcd\!\left(a, b\right) Greatest common divisor
DivisorSumknf(k)\sum_{k \mid n} f(k) Sum over divisors
Totientφ(n)\varphi(n) Euler totient function
ZZGreaterEqualZn\mathbb{Z}_{\ge n} Integers greater than or equal to n
Source code for this entry:
    Formula(Equal(Sum(GCD(n, k), For(k, 1, n)), DivisorSum(Mul(d, Totient(Div(n, d))), For(d, n)))),
    Assumptions(Element(n, ZZGreaterEqual(0))))

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2021-03-15 19:12:00.328586 UTC