Is $\phi (k_1) + \phi (k_2)+\phi (k_3) +...\phi (k_n)=gcd(m, n) $ ? k is divisor of m and n
53263
Show $\sum\limits_{d|n}\phi(d) = n$.
32344
Let $a,k,m$ be integers. Prove that $\gcd(ka,km) = k\gcd(a,m)$.
48251
Prove that if $n \in \mathbb{N}$, then $\sum_{d|n}{(d(n))^3}=(\sum_{d|n}{d(n)})^2$ where $d(n)$ is the divisor function.
84417
Prove that if $\gcd(a,b)=1$ then $\gcd(a^m, b)=1$
139833
Prove that $\gcd(M, N)\times \mbox{lcm}(M, N) = M \times N$.
102133
Prove: $\gcd(a,b) = \gcd(a, b + at)$.
190
Why $\gcd(qb+r,b)=\gcd(b,r)$?
156641
Show that $\gcd(3n,3n+ 2) = 1$ when $n$ is odd
59566
Proving that $ka \equiv kb \pmod{m} \iff a \equiv b \pmod{m/\gcd(k,m)}$
66748
Show that if $a \equiv b \pmod n$, $\gcd(a,n)=\gcd(b,n)$
85688
How to show $\gcd(ac, bd) = \gcd(a,d) * \gcd(b,c)$
53745
Euler's $\phi$ function: Find all $n$ such that $\phi(n)=n/3$
1197
Finding $\gcd(2n-1,2n+1)$ . . . I think it's 1 but is my logic right?
142693
$\gcd(a,b) = \gcd(a + b, \mathrm{lcm}[a,b])$
122096
Find $GCD(n^2+1,n+1)$
107095
Prove $\gcd(a,b) \gcd(a,c) \gcd(b,c) \,\text{lcm} (a,b,c)^2=$ $\text{lcm}(a,b)\,\text{lcm}(a,c) \,\text{lcm}(b,c) \gcd(a,b,c)^2$
66785
Find $\gcd(p^n-1,p^m+1)$.