（PAT乙级）1049 数列的片段和（C语言实现）
总结：这题主要考察的还是数学思维，找数学规律求和的问题。1、规律如下：若有n个数：{a1} {a1,a2} .....{a1,a2,...an}可以看出a1有n-1+1个，a2有n-2+1个，...，an有n-n+1个 {a2} {a2,a3}......{a2,a3,...,an}可以看出a2有n-2+1个，a3有n-3+1个，...，an有...
