myChar := Chr(66);                // Использование Char для конвертирования

const ci_interval = 26; {â àãë. ñëîâàðå 26 áóêàô:)}
      ci_index = $61; { èíäåêñ ñèìâîë "à" â ascii}

function IntToSymbols(Const bound : Cardinal) : String;
Var i, curBound, c_mod : Cardinal;
    c_tmp : Char;
Begin
    Result := '';
    curBound := bound;
    while true do
    Begin
        if curBound < ci_interval then
        Begin
            Result := Result + Chr(ci_index + curBound);
            Break;
        end;
        c_mod := curBound mod ci_interval;
        curBound := curBound div ci_interval;
        Result := Result + Chr(ci_index + c_mod);
    end;
    {ïåðåâîðà÷èâàåì ñòðîêó}
    for i := 1 to Length(Result) div 2 do
    Begin
        c_tmp := Result[i];
        Result[i] := Result[Length(Result)-i+1];
        Result[Length(Result)-i+1] := c_tmp;
    end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var i : Integer;
begin
    for i := 0 to *сколько надо вариантов* do
     Memo1.Lines.Add(IntToSymbols(i));
end;