# How to get list of relative primes for a given number?

How to get list of relative primes for a given number? Is there any direct sage function?

How to get list of relative primes for a given number?

How to get list of relative primes for a given number? Is there any direct sage function?

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2

There are indeed more direct ways to list integers coprime to a given integer in Sage.

One way is to build the ring of integers modulo `m`

, then list the multiplicative group of that ring.

```
sage: m = 8
sage: Zmod(m).list_of_elements_of_multiplicative_group()
[1, 3, 5, 7]
```

Note that this returns a list of Python integers:

```
sage: type(Zmod(m).list_of_elements_of_multiplicative_group()[0])
<class 'int'>
```

To get Sage integers one would need

```
sage: m = 8
sage: [ZZ(k) for k in Zmod(m).list_of_elements_of_multiplicative_group()]
[1, 3, 5, 7]
```

Check:

```
sage: [ZZ(k) for k in Zmod(m).list_of_elements_of_multiplicative_group()][0].parent()
Integer Ring
```

Another way is to use the method `coprime integers`

, which expects another argument
to say how far you want to list integers that are coprime to `m`

. To get them up to `m - 1`

:

```
sage: m = 8
sage: m.coprime_integers(m)
```

To get them further:

```
sage: m.coprime_integers(29) # list up to 29 (excluded)
[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27]
```

These are returned as Sage integers:

```
sage: m.coprime_integers(m)[0].parent()
Integer Ring
```

This suggests two improvements in Sage (I'll check if tickets exist, and open them if not):

- make
`list_of_elements_of_multiplicative_group`

return Sage integers - set a default argument value in the
`coprime_integers`

method of integers so that`m.coprime_integers()`

is equivalent to`m.coprime_integers(m)`

0

This is my custom function to get list of relative primes

```
def getRelativePrimeList(n):
L = [];
for i in range(1,n):
if gcd(i,n)==1:
L.append(i);
return L;
```

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Asked: ** 2019-02-02 15:25:02 +0100 **

Seen: **3,675 times**

Last updated: **Feb 03 '19**

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