# How to use Do and NestList combine?

g[x_]:=((i - 1/i)*x + (1/i)*(x/2))/2;


I want to find the following list

NumberForm[NestList[g, 0.8, 20], 16];


But don't know how to use "Do" for the values of i= {1,2,3,4,.....} varies with each step

Help would be very welcome

• Maybe g[x_, i_] := ((i - 1/i) x + (1/i) (x/2))/2; FoldList[g, 0.8, Range[20]] Apr 13, 2016 at 17:05
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– user9660
Apr 13, 2016 at 17:22

I assume that you want to obtain following list

{0.8,g[0.8 (*with i=1*)],g[g[0.8] (*with i=2*)]...}


One way:

g[x_, i_] := ((i - 1/i) x + (1/i) (x/2))/2;
FoldList[g, 0.8, Range[20]]


Another way, if you really want to use NestList

g2[{x_, i_}] := {((i - 1/i) x + (1/i) (x/2))/2, i + 1};
First@Transpose@NestList[g2, {0.8, 1}, 20]

• Thanks a lot Dear, but I think the sequence be look like {0.8,g[0.8 (with i=1)],g[g[0.8 (with i=1)] (with i=2)]...}, Is it the same one or will be different??? Apr 15, 2016 at 17:46
• @Marwat yes it is the same one. I just dropped there "with i=1" in my description. Apr 15, 2016 at 17:56