var max_count_item = Enumerable.Range(0, symbols.Length)
                    .Select(w => symbols.Skip(w)).
                    Select(w => new
                    {
                        Item = w.FirstOrDefault(),
                        ItemsAfterCount = w.TakeWhile(w2 => w2 == w.FirstOrDefault()).Count()
                    }).OrderByDescending(w => w.ItemsAfterCount).First();
                Console.WriteLine(String.Format("{0} встречается - {1} раз", max_count_item.Item, max_count_item.ItemsAfterCount));