$4$ vectors in $\mathbb{Z_4}^9$that sum to $0$.
123690
Olympiad question on Pigeonhole principle
28027
Find $\sum_{k=0}^{n}4^k \binom{n}{k}$
124240
Inductive proof of $\,9 \mathrel| 4^n+6n-1\,$ for all $\,n\in\Bbb N$
1162
Why $\{\mathbf{0}\}$ has dimension zero?
5049
Proving $\sum_{k=0}^n(-1)^k\binom nk=0$
21840
Zero divisors and units for the ring $\mathbb{Z}/n\mathbb{Z}$ with integer $n$
146990
How to find the number of automorphisms on $\mathbb Z_2\times \mathbb Z_4$
151390
Let $q_1,q_2,q_3,q_4$ be orthonormal vectors in $\mathbb{R}^4$,$z_1,z_2,...,z_6$ orthonormal vectors in $\mathbb{R}^6$ and $A=z_1q_1^T + z_2q_2^T$.
104509
The center of $A_n$ is trivial for $n \geq 4$
18198
Lang Algebra Chapter 6 Theorem 9.4
148343
The sum of the elements in a field of at least three elements is 0
128200
Sequence sum question: $\sum_{n=0}^{\infty}nk^n$
51800
We have matrix $A\in M_{n-1\times n}(\mathbb Z)$ so that the sum of entries in each row is zero. Prove that $\det(AA^T)=nk^2.$
56828
A combinatorial proof that the alternating sum of binomial coefficients is zero
90519
Combinatorial proof of $\sum\limits_{k=0}^n {n \choose k}3^k=4^n$
10606
Finding how multiplication and addition behave on $\mathbb{F}_4$ without any result
61987
$x^2+1=0$ in $\mathbb{Z}_7$