The sequence "1, 3, 5, 7, 9, 11, 13, 15, 17, 19" consists of the first ten odd numbers. Odd numbers are integers that cannot be evenly divided by 2, meaning they always leave a remainder of 1 when divided. This sequence starts at 1 and increases by 2 each time. Odd numbers are often used in various mathematical concepts and can be found in everyday situations, such as counting items or determining seating arrangements. They are also important in number theory, where they are studied for their unique properties and relationships with even numbers, like 2, 4, 6.