Hello,

I was wondering the difference between Sage's spherical_harmonic (as well as Maxima's spherical_harmonic) and Mathematica's SphericalHarmonicY for the same arguments.

Sage's

```
print(spherical_harmonic(1,1,pi/3,pi/6).n())
print(spherical_harmonic(1,-1,pi/3,pi/6).n())
```

gives the following results:

```
0.149603355150537 - 0.259120612103502*I
-0.259120612103502 + 0.149603355150537*I
```

Maxima's

```
print(maxima.spherical_harmonic(1,1,pi/3,pi/6).n())
print(maxima.spherical_harmonic(1,-1,pi/3,pi/6).n())
```

gives

```
0.259120612103502 + 0.149603355150537*I
-0.259120612103502 + 0.149603355150537*I
```

and Mathematica,

```
SphericalHarmonicY[1, 1, Pi/3, Pi/6] // N
SphericalHarmonicY[1, -1, Pi/3, Pi/6] // N
```

gives

```
-0.259121 - 0.149603*I
0.259121 - 0.149603*I
```

I have come across the convention difference between Maxima and Mathematica in some textbooks-- that is the (-1)^m factor, but I am not quite sure if I get it for between Sage's and Mathematica's.

So, **what is the mathematical relationship between Sage's spherical_harmonic and Mathematica's SphericalHarmonicY ?**

Thanks alot.