数列解析一个数列 1,2,3,x, 1,2,3,x, 1,2,3,x, yx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
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![数列解析一个数列 1,2,3,x, 1,2,3,x, 1,2,3,x, yx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](/uploads/image/z/4349041-25-1.jpg?t=%E6%95%B0%E5%88%97%E8%A7%A3%E6%9E%90%E4%B8%80%E4%B8%AA%E6%95%B0%E5%88%97+1%2C2%2C3%2Cx%2C++++++++++++++++1%2C2%2C3%2Cx%2C++++++++++++++++1%2C2%2C3%2Cx%2C+++++++++++++++++yx%E7%9A%84%E6%84%8F%E6%80%9D%E6%98%AF%E5%90%8E%E9%9D%A2%E8%BF%98%E6%9C%894%2C5%E4%B8%8D%E7%A1%AE%E5%AE%9A%2Cy%E7%9A%84%E6%84%8F%E6%80%9D%E6%98%AF%E8%BF%98%E6%9C%89n%E4%B8%AA1%2C2%2C3%2Cx%2C%E7%9A%84%E6%83%85%E5%86%B5.%E6%80%8E%E6%A0%B7%E6%8A%8A%E9%87%8C%E8%BE%B9%E7%9A%841%E3%80%812%E3%80%813%E3%80%81x%E5%88%86%E5%BC%80%E5%8F%96%E5%87%BA%E6%9D%A5%3F+%E6%B1%82%E7%AE%97%E6%B3%95%2C%E8%B0%A2%E8%B0%A2%E5%90%84%E4%BD%8D)
数列解析一个数列 1,2,3,x, 1,2,3,x, 1,2,3,x, yx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
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.
数列解析一个数列 1,2,3,x, 1,2,3,x, 1,2,3,x, yx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
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+2c)-(b+c)=c.
b = 1-c=1.
a(n) = 1 + n-1 = n.
x = a(4) = 4.
a(n) = 1+b(n-1)+c(n-1)^2 + d(n-1)^3,
1 = a(1),
2 = a(2) = 1 + b + c + d, 1 = b+c+d.
3 = a(3) = 1 + 2b + 4c + 8d, 1 = b + 2c + 4d, 0 = 1-1=(b+2c+4d)-(b+c+d)=c+3d, c = -3d.
b = 1 - c - d = 1+2d.
a(n) = 1 + (1+2d)(n-1)-3d(n-1)^2 + d(n-1)^3,
a(2) = 1 + (1+2d) - 3d + d = 2,
a(3) = 1 + 2(1+2d) - 12d + 8d = 3,
a(4) = 1 + 3(1+2d) - 27d + 27d = 4 + 6d = x,
由于d可有无穷种取值,因此x=4+6d,也有无穷种取值.