£¨2013•ËɽÇøһģ£©¶¨Òå±ä»»T½«Æ½ÃæÄڵĵãP£¨x£¬y£©£¨x¡Ý0£¬y¡Ý0£©±ä»»µ½Æ½ÃæÄڵĵã
Q(£¬)£®
ÈôÇúÏß
C0£º+=1(x¡Ý0£¬y¡Ý0)¾±ä»»TºóµÃµ½ÇúÏßC
1£¬ÇúÏßC
1¾±ä»»TºóµÃµ½ÇúÏßC
2¡£¬ÒÀ´ËÀàÍÆ£¬ÇúÏßC
n-1¾±ä»»TºóµÃµ½ÇúÏßC
n£¬µ±n¡ÊN
*ʱ£¬¼ÇÇúÏßC
nÓëx¡¢yÖáÕý°ëÖáµÄ½»µãΪA
n£¨a
n£¬0£©ºÍB
n£¨0£¬b
n£©£®Ä³Í¬Ñ§Ñо¿ºóÈÏΪÇúÏßC
n¾ßÓÐÈçÏÂÐÔÖÊ£º
¢Ù¶ÔÈÎÒâµÄn¡ÊN
*£¬ÇúÏßC
n¶¼¹ØÓÚÔµã¶Ô³Æ£»
¢Ú¶ÔÈÎÒâµÄn¡ÊN
*£¬ÇúÏßC
nºã¹ýµã£¨0£¬2£©£»
¢Û¶ÔÈÎÒâµÄn¡ÊN
*£¬ÇúÏßC
n¾ùÔÚ¾ØÐÎOA
nD
nB
n£¨º¬±ß½ç£©µÄÄÚ²¿£¬ÆäÖÐD
nµÄ×ø±êΪD
n£¨a
n£¬b
n£©£»
¢Ü¼Ç¾ØÐÎOA
nD
nB
nµÄÃæ»ýΪS
n£¬Ôò
Sn=1ÆäÖÐËùÓÐÕýÈ·½áÂÛµÄÐòºÅÊÇ
¢Û¢Ü
¢Û¢Ü
£®