Showing what's behind the curtain

Rooms of Doom

Count the number of horizontal, vertical and diagonal rectangles in a rectangular grid

Determine if the origin is contained inside a triangle.

Find the smallest member of the longest amicable chain

Find a set of terms that produce longest set of consecutive digits

Find the largest square number formed by pairs of encoded anagrams.

Investigate the optimum polynomial function to model the first `k` terms of a given sequence.

Find a minimum path sum in a matrix from the top left to the bottom right corners by moving up, down, left or right.

Find the 2000th hexagonal tile in which the differences between it and its 6 neighbors yield 3 primes.

Find the sum of the perimeters of all *almost equilateral triangles* with integral side lengths and area.