π/4 = 1 − 1/3 + 1/5 − 1/7 + … Calculus textbooks call this the Leibniz series (1673). The Tantrasaṅgraha, composed in Kerala around 1500 CE, states the same alternating series as a Sanskrit verse rule — then adds a correction term that repairs its notoriously slow convergence. Kerala's own commentaries credit the series to Mādhava of Saṅgamagrāma (c. 1340–1425), placing the result roughly three centuries before Leibniz published it in Europe.