This function generates root Zadoff-Chu sequence of complex symbols as per LTE specifications.
SEQ = LTEZADOFFCHUSEQ(R, N) generates the Rth root Zadoff-Chu sequence (SEQ) of length N.
3rd Generation Partnership Project, Technical Specification Group Radio
Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA),
Physical channels and modulation, Release 10, 3GPP TS 36.211, v10.0.0,
2010-12.