On Jun 7, 11:05 ¨Âí¬ ¢ÅòéÉ®¼òõâùôòáéî®®®Àçíáéì®ãïí¾ ÷òïôåº > By the way, if there are n people, I believe the formula for the > number of partnership schemes is: > > n! / (n / 2)! / 2**(n / 2) An alternative (and more efficient) way to compute the number of partnership schemes is to multiply all the odd values from 1..n. For example, if there are eight people, then we have 1 * 3 * 5 * 7, or 105. Eric ==== LearnRuby.com offers Rails & Ruby HANDS-ON public & ON-SITE workshops. ¨ÂõâÆõîäáíåîôáìó ×ëóè ¨Âõî±¶±ÁîÁòâïò¬ Íéãè ¨Âåáäù æïÒáéìÒõâù ×ëóèÊõîå ²³²ÁîÁòâïò¬ Íéãè ¨Âõâïî Òáéì×ëóè ¨Âõî²µ²Áîîòâïò¬ Íéãè ¨ÂõâÐìõó ÒáéìÃïíâ×ëóè ¨Âõî²³²ÁîÁòâïò¬ Íéãè Please visithttp://LearnRuby.comfor all the details.