Compute the rotation matrix d(pi/2) used in rotating data expressed in spherical harmonics.
dj = djpi2 (lmax)
dj : float, dimension (lmax+1, lmax+1, lmax+1)
: The rotation matrix dj(pi/2).
lmax : integer
: The maximum spherical harmonic degree of the spherical harmonic rotation.
djpi2 will calculate the rotation matrix d_{mM}^j (pi/2) that is used in rotating spherical harmonics in the routines SHRotateRealCoef and SHRotateCoef.
This routine is based on code originally written by Guy Masters.