series - similar things placed in order or happening one after another; "they were investigating a series of bank robberies"

arithmetic progression - (mathematics) a progression in which a constant is added to each term in order to obtain the next term; "1-4-7-10-13- is the start of an arithmetic progression"

geometric progression - (mathematics) a progression in which each term is multiplied by a constant in order to obtain the next term; "1-4-16-64-256- is the start of a geometric progression"

harmonic progression - (mathematics) a progression of terms whose reciprocals form an arithmetic progression