数列解析

题目

数列解析
一个数列 1,2,3,x,
1,2,3,x,
1,2,3,x,
y
x的意思是后面还有4,5不确定,y的意思是还有n个1,2,3,x,的情况.怎样把里边的1、2、3、x分开取出来? 求算法,谢谢各位大牛.

答案

a(n) = 1 + b(n-1),1 = a(1) 2 = a(2) = 1+ b, b=1.a(n) = 1 + n-1 = n.3 = a(3). x = a(4)=4.a(n) = 1 + b(n-1) + c(n-1)^2,1 = a(1),2 = a(2) = 1+ b+c, 1 = b+c.3 = a(3) = 1 + 2b + 4c, 1 = b+2c, 0 = 1-1 = (b+...