Hello, Otto (thanx for your interest) - i change a description of a problem, hope now it's more understandable.

Hello Alexey,

I changed your notebook a bit, have a look at this piece of code:

ClearAll["Global`*"]

a = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
For[i = 2, i <= Length[a], i++,
 b = Select[a, # < 2 a[[i]] || # > 3 a[[i]] &];
 Print[i, ",", b];
 Print["####  ", a];
 a = Complement[a, b];
 Print["****  ", a]]

Basically you need to seperate your commands with a semicolon (;). In general one should try to avoid For-loops and this infamous Print command; better would be a more functional style and e.g. a Reap - Sow constuct for returning values as in my example above.

Regards -- Henrik

Hi Ampo,

I am not sure: Could this be a minimal example of what you are intending?

ClearAll["Global`*"]

a = Range[10];
result = Reap[While[Length[a] > 1,
     (* calculation of a specific index, e.g.: *)
     fIndx = 1 + Ceiling[(Length[a] - 1) Abs[Sin[Length[a]]]];
     (* calculation of depending sublist: *)
     subA = RandomSample[Range[fIndx], 2];
     (* removing elements of sublist from list: *)
     a = Complement[a, a[[subA]]];
     Sow[a]]][[2, 1]];

result // TableForm

Regards -- Henrik