Mathematical discussion of the Number Pyramid had arisen in the context of Indian studies of combinatorics and of binomial numbers and Greeks' study of figurate numbers. At around the same time it was discussed in Persia (Iran) by the Persian mathematician Al-Karaji. It was later repeated by the Persian poet-astronomer-mathematician Omar Khayyám. Several theorems related to the triangle were known including the binomial theorem. Khayyam used a method of finding nth roots based on the binomial expansion and therefore on the binomial coefficients. It was known in China in the early 11th century through the work of the Chinese mathematician Jia Xian. In the 13th century Yang Hui presented the triangle.