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6'' Squares
In mathematics, a square number, sometimes also called a perfect square, is an integer that can be written as the square of some other integer; in other words, it is the product of some integer with itself. So, for example, 9 is a square number, since it can be written as 3 Γ 3. more...
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Square numbers are non-negative. Another way of saying that a (non-negative) number is a square number, is that its square root is again an integer. For example, β9 = 3, so 9 is a square number.
A positive integer that has no perfect square divisors except 1 is called square-free.
The usual notation for the formula for the square of a number n is not the product n Γ n, but the equivalent exponentiation n2, usually pronounced as "n squared". For a non-negative integer n, the nth square number is n2, with 02 = 0 being the zeroth square. The concept of square can be extended to some other number systems. If rational numbers are included, then a square is the ratio of two square integers, and, conversely, the ratio of two square integers is a square (e.g., 4/9 = (2/3)2).
Starting with 0, there are 1 + ββmβ square numbers up to and including m.
Examples
The first 50 squares of natural numbers (sequence A000290 in OEIS) are:
Properties
The number m is a square number if and only if one can arrange m points in a square:
The formula for the nth square number is n2. This is also equal to the sum of the first n odd numbers
as can be seen in the above pictures, where a square results from the previous one by adding an odd number of points (marked as '+'). So for example, 52 = 25 = 1 + 3 + 5 + 7 + 9.
The nth square number can be calculated from the previous two by doubling the (n β 1)-th square, subtracting the (n β 2)-th square number, and adding 2, because n2 = 2(n β 1)2 β (n β 2)2 + 2. For example, 2Γ52 β 42 + 2 = 2Γ25 β 16 + 2 = 50 β 16 + 2 = 36 = 62.
It is often also useful to note that the square of any number can be represented as the sum 1 + 1 + 2 + 2 + ... + n β 1 + n β 1 + n. For instance, the square of 4 or 42 is equal to 1 + 1 + 2 + 2 + 3 + 3 + 4 = 16. This is the result of adding a column and row of thickness 1 to the square graph of three (like a tic tac toe board). You add three to the side and four to the top to get four squared. This can also be useful for finding the square of a big number quickly. For instance, the square of 52 = 502 + 50 + 51 + 51 + 52 = 2500 + 204 = 2704.
Read more at Wikipedia.org
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