Prompting Challenge: A Simple Repeating Shape

So this is a bit random, but I spent a few hours this weekend trying to get an AI - dozens of prompts against all of the major image models - to generate this exact line drawing. Theoretically, it should be easy and straightforward: 7 equilateral triangles, joined in a ring to form an outer heptagon. Nothing more, nothing less. And yet, my results have been miserable... including 14-sided shapes, triangles that aren't equilateral, squares in the mix, etc.

Anyway, I figured I'm just prompting wrong, and would open it up to smarter people to try their luck at it :)