Art of Problem Solving
AoPS Online
Math texts, online classes, and more
for students in grades 5-12.
Visit AoPS Online ‚
Books for Grades 5-12 Online Courses
Beast Academy
Engaging math books and online learning
for students ages 6-13.
Visit Beast Academy ‚
Books for Ages 6-13 Beast Academy Online
AoPS Academy
Small live classes for advanced math
and language arts learners in grades 2-12.
Visit AoPS Academy ‚
Find a Physical Campus Visit the Virtual Campus

User talk:Baijiangchen

Revision as of 00:25, 22 July 2012 by Saprmarks (talk | contribs)

If:

$W(0):=1$

$W(n):=\sum_{i=0}^{n-1}({n-1 \choose i}W(i)(x-i-1)!(2^{x-i-1}))$

Then:

$W(n)=(2n-1)!!$

Sam's stuff

Let $W(n)=\sum_{i=1}^{n}(\binom{i-1}{n-1}W(i-1)(x-i)!(2^{x-i}))$

Retrieved from "https://artofproblemsolving.com/wiki/index.php?title=User_talk:Baijiangchen&oldid=47700"