sorry, floor 18th's answer is wrong,
this is much more complex than i have thought,

but floor 16th is also wrong,
f0=0,f1=1,f2=3,f3=5,f4=9,f5=13,   f'3=7,f'4=15

f(n+1)=min{f(m)+f(n-m)}*2+1  ???
f(2k+1)=(2*f(k))*2+1, f(2k)=(f(k-1)+f(k))*2+1

f6=(f3+f2)*2+1=17,     f7=f3*4+1=21?,
f7=25,  f7=(f4+f2)*2+1=25, f7=(f3+f'3)*2+1=25
f8=(f4+f'3)*2+1=33, f8=(f5+f2)*2+1=33,
f9=(f5+f'3)*2+1=41, f9=(f6+f2)*2+1=41,
f10=(f6+f'3)*2+1=49, f10=(f7+f2)*2+1=57?
tomorrow continue,

well, the answer is f30=1025, and i find the formula: n=k(k+1)/2, f(n)=2^k*(k-1)+1, f(n+m)=2^k*(k+m-1)+1,1<=m<=k+1. the proof is complex, so i don't write it out here

[em77]
alan_delon用了两种陋笔不多懂的方法解这道题,
英文和高数.但看到1025,是对了.
陋笔的答案不可视为公式,但可行,
当有r支杆,2的n-1次方折点在n+r-2cr-1处.
但既有简单公式可用,也不必研究陋笔这个老土方法了.
呵呵.............................

当有r支杆,2的n-1次方折点在n+r-2cr-1处.

what's the meaning of it?

1025？

折腾半天，还是跟4楼一样的答案，
呵呵......................

引用:

以下是引用[I]儿死散巫酒[/I]在2006-8-11 3:15:06的发言：[BR]折腾半天，还是跟4楼一样的答案，
呵呵......................

but you don't find out the general formula, that's quite different

陋笔不懂你们用的方法,陋笔的老土方法也不必先解释了.
却想知道,是否一经套用,任何情况都能解决.
假设这题是50个环,7支杆,答案会是多少?

引用:

以下是引用[I]陋笔[/I]在2006-8-11 15:06:26的发言：[BR]陋笔不懂你们用的方法,陋笔的老土方法也不必先解释了.
却想知道,是否一经套用,任何情况都能解决.
假设这题是50个环,7支杆,答案会是多少?

well, the general formula exist,
have the column number is M, the circle number is N,
i have given the general formula when M=4 on the 22nd floor,
and, for the general M, the formula is very complex,  so i don't write it out here,
but i can give you the answer of F7(50)

AD you really think I got the answer by simple counting? LOL...
俩人你不懂我的意思，我不懂你的意思，so funny~~~