a sequence (= an ordered series of numbers) in which the numbers get bigger or smaller by the same a

中文解释

算术级数，等差数列，其中任何相邻两项以相同数量递增或递减，如3,6,9…, 或9,6,3 A computer search revealed an arithmetic progression consisting of 23 primes, the longest such sequence yet found. 电脑搜索显示了一个由 23 个素数组成的等差数列，这是迄今为止发现的最长的此类数列。