Problem1855--C二级辅导-等差数列

1855: C二级辅导-等差数列

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 1  Solved: 1
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Description

sum=2+5+8+11+14+…，输入正整数n，求sum的前n项和。

Sample Input Copy 

2

Sample Output Copy 

7

Source/Category

 
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