How do you find out square numbers?

generally you would multiply a number by itself, but i have found out a marvelous trick, and it is pretty easy since I am only a child, but starting with 1, if you add three, you get four, the next square number. then you add five to get nine the next square number, then seven to get sixteen and so on. So in simpler terms you take one and add three to get the next square number, then add five, then seven counting by odd numbers. Here is an equation. the bold numbers are the square numbers and the Italic numbers are the progressing odd numbers.

1+3= 4+5= 9+7=16and so on.