Tricky Triangle Trivia

Callum FloumeAPLLeave a Comment

For this week’s problem we’ve sought inspiration from Project Euler. I’ve been working through the problems there and got the group involved where I’ve struggled. This particular problem is one that we’ve yet to find a satisfying solution to. So we’re looking to the APL community for help.

Highly divisible triangular number

Problem 12
The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:

1, 3, 6, 10, 15, 21, 28, 36, 45, 55, …

Let us list the factors of the first seven triangle number:


1: 1
 3: 1,3
 6: 1,2,3,6
10: 1,2,5,10
15: 1,3,5,15
21: 1,3,7,21
28: 1,2,4,7,14,28