Square of $7+\sum_{k=1}^n6\times10^k$
41571
Prove that in a sequence of numbers $49 , 4489 , 444889 , 44448889\ldots$
131708
Sum of powers of natural numbers
41789
Fermat's theorem on sums of two squares
17390
Find $LK_1^2 + LK_2^2 + \dots + LK_{11}^2$.
138548
For what pair of integers $(a,b)$ is $3^a + 7^b$ a perfect square.
117200
Evaluation of $ \sum_{k=0}^n \cos k\theta $
138081
How to determine whether a number can be written as a sum of two squares?
37603
Finding the Integer part of $\sum_{k=2} ^{9999}\frac{1}{\sqrt k}$
126105
Compute $\sum_{k=1}^{n} \frac 1 {k(k + 1)} $
35525
Methods to compute $\sum_{k=1}^nk^p$ without Faulhaber's formula
143540
How to prove this decomposition of sum of squares?
17194
$6^{(n+2)} + 7^{(2n+1)}$ is divisible by $43$ for $n \ge 1$
37007
Evaluating $\sum_{k=1}^{n} \frac{1}{k(k+1)}$
48200
Simplify $\sum_{i=0}^n (i+1)\binom ni$
125040
Show by induction : $n^7-n$ is a multiple of 7
128584
Sum of squared quadratic non-residues
29099
Let consider a square $10$x$10$ and write in the every unit square the numbers from $1$ to $100$