O OO OOO OOOO 由上而下第N行有多少个
问题描述：
O OO OOO OOOO 由上而下第N行有多少个
答
nge
答
It’s been a long time since I came around
It’s been a long time but I’m back in town
But this time i'm not leaving without you
You taste like whiskey when you kiss me oh
I'll give anything again to be your baby doll
Yeah this time I'm not leaving without you.
答
有n个.
答
o oo ooo oooo oooooooo 第1行1根， 第2行2根， 一共有N行的话， 总根数 = 1 + 2 + + N = N(N+1)/2 钢材如果排成梯形的