Ordinals were introduced by Georg Cantor in 1897 to accommodate infinite sequences and to classify sets with certain kinds of order structures on them. He discovered them by accident while working on a problem concerning trigonometric series—see Georg Cantor. ω, ω + 1, ω + 2, …, ω·2, ω·2 + 1, …, ω2, …, ω3, …, ωω, …, ωωω, …, ε0, ….