1-Gonal Number Evolution [ -14 → -20 ]

Instructions

What if polygonal numbers went below triangle numbers (3-gonal)? Here's the sequence of 1-gonal numbers. The sequence goes as 0, 1, 1, 0, -2, -5, -9, -14, etc. After the first few numbers, numbers start going negative. Although 2-gonal numbers would be called lines since lines have 2 vertices, like triangles are 3-gons that have 3 vertices, 2-gonal numbers aren't really needed since they have the formula n(0n+1), which equals n and therefore is the natural number sequence. 1-gonal numbers have the formula of n(3-n)/2.