Find numbers of the form $\frac{n(n+1)}{2}$ such that the digits of the number are all same
136885
Series of natural numbers which has all same digits
142008
Find all natural numbers $n$ such that ${(n+1)}^{1/2}-{(n-1)}^{1/2}$ is rational
113331
Number of ways a natural number can be written as sum of smaller natural number
110958
How to solve for any given natural number n?
108919
Numbers till 400 divisible by 2, 3, 5, 7
25181
Simple numerical methods for calculating the digits of $\pi$
87626
Why are all $n$, s.t. the sum of digits of $n$ and $n^2$ coincide, $\equiv 0,1 \bmod 9$
127446
How do we find a fraction with whose decimal expansion has a given repeating pattern?
143620
How many $n$-digit decimal sequences (using the digits $0 = 9$) are there in which the digits $1$, $2$ and $3$ all appear?
148703
Permutations with repeating digits
121554
Finding $\sum\frac{1}{2^n(n+1)}$
139350
Given two coprime integers, find multiples of them that differ by 1
21612
How to prove this form of $n$?
27427
Arranging numbers from $1$ to $n$ such that the sum of every two adjacent numbers is a perfect power
20988
Notation for specifying the fractional part of a number
123117
Is it possible to find $n-1$ consecutive composite integers
48655
Find all n such that : $3 \mid (n2^{n}+1)$