n=3, p=1-p=1/2.
Binomial expansion: "1 3 3 1" p^3, 3p^2(1-p), 3p(1-p)^2, (1-p)^3: 1/8, 3/8, 3/8, 1/8.
Table gives: P(3H)=P(3T)=0.125; P(2H,1T)=P(1H,2T)=3/8. (H=head, T=tail).
P(2H,1T or 1H,2T)=3/8+3/8=3/4.
P(at least one head)=1-P(no heads)=1-1/8=7/8=P(at least one tail).