http://en.wikipedia.org/wiki/Square-free_integer

In mathematics, a square-free, or quadratfrei, integer is one divisible by no perfect square, except 1. For example, 10 is square-free but 18 is not, as it is divisible by 9 = 32. The smallest square-free numbers are
1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, ... (sequence A005117 in OEIS)

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http://mathworld.wolfram.com/Squarefree.html

A number is said to be squarefree (or sometimes quadratfrei; Shanks 1993) if its prime decomposition contains no repeated factors. All primes are therefore trivially squarefree. The number 1 is by convention taken to be squarefree. The squarefree numbers are 1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, ... (Sloane's A005117). The squareful numbers (i.e., those that contain at least one square) are 4, 8, 9, 12, 16, 18, 20, 24, 25, ... (Sloane's A013929).

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http://www.research.att.com/~njas/sequences/A...

Square-free numbers: numbers that are not divisible by a square greater than 1.
1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102, 103, 105, 106, 107, 109, 110, 111, 113

COMMENT
1 together with the numbers that are products of distinct primes.


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http://de.wikipedia.org/wiki/Quadratfrei
Quadratfrei

Eine natürliche Zahl heißt quadratfrei, wenn es außer der Eins keine Quadratzahl gibt, die diese Zahl teilt. Anders formuliert tritt in der eindeutigen Primfaktorzerlegung n =p_1 \cdot ...\cdot p_k einer quadratfreien Zahl keine Primzahl mehr als einmal auf.

Beispielsweise ist die Zahl 6= 2\cdot 3 quadratfrei, während 54 = 2 \cdot 3^2 \cdot 3 nicht quadratfrei ist. Die ersten quadratfreien Zahlen sind
1, 2, 3, 5, 6, 7, 10, 11, 13, 14, … (Folge A005117 in OEIS)