A triangular number is one that fits the formula n (n+1)/2, such as 1, 3, 6, 10, 15. Even if I told you Harry’s triangular number you would not be able to deduce with certainty which perfect ...

Test your knowledge of taxicab geometry, triangular numbers, the golden ratio and more. Credit... Supported by By Steven Strogatz “Math, Revealed,” our four-part series exploring the ...

I have in mind three numbers. Each is a multiple of 3 and consists of three different non-zero digits, just one of which is 3. For each of these numbers individually, three of the following six ...