n:=9;;
L:=List([1..n],i->List([1..n],j->0));
pos_max:=0;

Backtracking:=function(j)
  local i,r,c,s,clash;

  # Print(L,"\n");

  for i in [1..n] do
    clash := false;

    # fill in diagonal
    for r in [1..n] do
      c := ((j+r-2) mod n) + 1;
      s := ((i+r-2) mod n) + 1;
      L[r][c] := s;

      # repeated symbol in row
      if(ForAny([1..r-1],r2->L[r2][c]=s)) then clash:=true; continue; fi;

      # repeated symbol in col
      if(ForAny([1..c-1],c2->L[r][c2]=s)) then clash:=true; continue; fi;

      # repeated symbol in antidiagonal
      if(ForAny([2..n],k->L[((r-k) mod n) + 1][((c+k-2) mod n) + 1]=s)) then clash:=true; continue; fi;
    od;

    if(clash <> true) then
      if(j>pos_max) then
        Print("Best thus far: ",L,"\n");
        pos_max := j;
      fi;

      if(j=n) then
        Print(L,"\n");
      else
        Backtracking(j+1);
      fi;
    fi;

    for r in [1..n] do
      c := ((j+r-2) mod n) + 1;
      L[r][c] := 0;
    od;
  od;
end;;

Backtracking(1);