算术级数

arithmetic series (such as 2+4+6+8+...)

to regard as / to figure / to calculate / to compute

arithmetic / sums (mathematics as primary school subject)

method / technique

various genera of flowers of Asteracea family (daisies and chrysanthemums), including Atractylis lancea

level / grade / rank / step (of stairs) / CL:個|个[ge4] / classifier: step, level

(math.) series

to count / to count as / to regard as / to enumerate (sb's shortcomings)

number / figure / several / CL:個|个[ge4]

frequently / repeatedly