1等差数列, arithmetic progression 2等比数列, geometric progression 3数列求和, dynamic series summing4公比, common ratio 5公差, common difference 6首项, leading term 7通项公式, general term formula 8最大项, maximum term 9最小项, minimum term 10递增数列,progressive increase series 11递减数列, diminishing series 12第n项, n-th term13取值范围value range