I don't know if I'm answering your question right but how I see the pattern is that a side is added to a shape after circle.
a triangle has 3 sides and then it goes to circle which is all round, then it goes to square, which has 4 sides. So it could be
triangle, circle, square, circle, pentagon, circle, hexagon, circle, heptagon, circle, octagon
sorry if I wasn't much help.
