  For numerical sequences taking values $0$ or complex numbers of modulus $1$,
we define Chowla property and Sarnak property. We prove that Chowla property
implies Sarnak property. We also prove that for Lebesgue almost every
$\beta>1$, the sequence $(e^{2\pi \beta^n})_{n\in \mathbb{N}}$ shares Chowla
property and consequently is orthogonal to all topological dynamical systems of
zero entropy. It is also discussed whether the samples of a given random
sequence have Chowla property almost surely. Some dependent random sequences
having almost surely Chowla property are constructed.
