Using For to generate a sequence

Question

I want to find the smallest positive integer $k$ such that the finite list s[k*m] contains no odd numbers, for $m=1,2 \dots$. Unfortunately FindInstance is not working for me, so I am trying to use a For loop instead.

Right now, I have the loop For[k=1, Length[Select[s[k*m],OddQ]]!= 0, k++, x = k+1 ].

After I specify $m$ (say I set m=3) and run the above, I will have x equal to the number I want. However, if I want the next number, I must specify m=4, run the above again, and request x again.

This is quite tedious. Is there a way, similar to Table, to get the sequence I am looking for, for $m$ ranging from $1$ to some specified upper bound?

Answer 1

Here is a solution with NestWhile.

To get a list:

Block[{s},
 s[l_] := 
  BlockRandom[SeedRandom[l]; 
   RandomChoice[{0.999, 0.001} -> {0, 1}, l]];
 
 Table[
  NestWhile[# + 1 &, 0, And @@ EvenQ[s[m #]] - 1 &],
  {m, 10}]
 ]

(*  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}  *)

To get an association:

Block[{s},
 s[l_] := 
  BlockRandom[SeedRandom[l]; 
   RandomChoice[{0.999, 0.001} -> {0, 1}, l]];
 
 AssociationMap[
  Function[m,
   NestWhile[# + 1 &, 0, And @@ EvenQ[s[m #]] &] - 1
   ],
  Range@10]
 ]
(*
  <|1 -> 51, 2 -> 25, 3 -> 21, 4 -> 12, 5 -> 22, 
    6 -> 10, 7 -> 31, 8 -> 11, 9 -> 8, 10 -> 11|>
*)

To prevent runaway computations:

Block[{s, $maxIterations = 10}, (* 10000 might be a reasonable setting *)
 s[l_] := 
  BlockRandom[SeedRandom[l]; 
   RandomChoice[{0.999, 0.001} -> {0, 1}, l]];
 
 AssociationMap[
  Function[m,
   NestWhile[# + 1 &, 0, And @@ EvenQ[s[m #]] &, 1, $maxIterations] - 1 /.
     $maxIterations - 1 -> "$maxIterations"
   ],
  Range@10]
 ]