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National and Regional Contests
PEN Problems
PEN J Problems
2
2
Part of
PEN J Problems
Problems
(1)
J 2
Source:
5/25/2007
Show that for all
n
∈
N
n \in \mathbb{N}
n
∈
N
,
n
=
∑
d
∣
n
ϕ
(
d
)
.
n = \sum^{}_{d \vert n}\phi(d).
n
=
d
∣
n
∑
ϕ
(
d
)
.
real analysis
function
group theory
abstract algebra
Divisor Functions