Showing what's behind the curtain

Comparing four-sided and six-sided dice

Find the smallest odd composite that cannot be written as the sum of a prime and twice a square.

Finding the number of blue discs for which there is 50% chance of taking two blue.

Compose Champernowne’s constant

What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?

Find a quadratic formula that produces the maximum number of primes for consecutive values of n.

Find the sum of the digits in 100!

Sum of the digits in 2^1000.

Find the greatest product of four adjacent numbers in the same direction in a grid.

Find the smallest number divisible by each of the numbers 1 to 20.