  In this paper, we determine the 4-adic complexity of the balanced quaternary
sequences of period $2p$ and $2(2^n-1)$ with ideal autocorrelation defined by
Kim et al. (ISIT, pp. 282-285, 2009) and Jang et al. (ISIT, pp. 278-281, 2009),
respectively. Our results show that the 4-adic complexity of the quaternary
sequences defined in these two papers is large enough to resist the attack of
the rational approximation algorithm.
