Harry and Tom have each found a 4-digit perfect square, a 3-digit perfect cube and a 3-digit triangular number that use 10 different digits, but with no leading zero. A triangular number is one that ...

The first four triangular numbers are 1, 3, 6 and 10, and the nth triangular number is given by the expression n(n+1)/2, so the 20th such number is 20 × 21 ÷ 2 = 210. ENIGMA is a triangular ...

Have you ever given thought to the number, 105? To some, it is just a number. To others, it may be the number of a highway or road. To a math professor, 105 is a triangular number, a dodecagonal ...