  The probability number distribution function of binary black hole mergers
observed by LIGO/Virgo O3a has double peaks as a function of chirp mass $M_c$,
total mass $M_t$, primary black hole mass $M_1$ and secondary one $M_2$,
respectively. The larger chirp mass peak is at $M_c \cong 30 M_{\odot}$. The
distribution of $M_2$ vs. $M_1$ follows the relation of $M_2\cong 0.7M_1$. For
initial mass functions of Population III stars in the form of $f(M) \propto
M^{-\alpha}$, population synthesis numerical simulations with $0\leq \alpha
\leq 1.5$ are consistent with O3a data for $M_c \gtrsim 20M_{\odot}$. The
distribution of $M_2$ vs. $M_1$ for simulation data also agrees with $M_2\cong
0.7M_1$ relation of O3a data.
