Finding a digit in the sequence of all natural numbers.
45788
$n$-th digit in the sequence of natural numbers
11359
Determine the Set of a Sum of Numbers
108563
Detecting consecutive integers in a list
49987
Gets last digit of a number
149716
Prove that $ \sqrt{n(n+1)(n+2)(n+3)+1} $ is always a natural number
131708
Sum of powers of natural numbers
43044
All natural numbers are equal.
156242
As many even numbers as natural numbers.
41571
Prove that in a sequence of numbers $49 , 4489 , 444889 , 44448889\ldots$
73020
Every integer is congruent to the sum of its digits mod 9
60706
Proof that there are infinitely many prime numbers starting with a given digit string
143620
How many $n$-digit decimal sequences (using the digits $0 = 9$) are there in which the digits $1$, $2$ and $3$ all appear?
83421
Checking if a number is a Fibonacci or not?
33705
Is $0$ a natural number?
78905
Calculate the factorial of an arbitrarily large number, showing all the digits
39391
IMO 2005 No 4. : All integers relatively prime to terms of infinite sequence
113950
Formula for reversing digits of positive integer $n$