seqn<-function(n=5,N=100,p=0.5){ #　N回のうちn回以上続けて表がでるか？
rn=rbinom(N,1,p)
count=0
for(i in 1:N){
if(rn[i] & count<n){
count=count+1
}
else{
if(count==n) {return(TRUE)}
else{
count=0
}
}
}
return(count==n)
}
mean(replicate(10^5,seqn()))

f <- function(n) mean(replicate(10^4,seqn(n)))
nn=2:20
yy=sapply(nn,f)
plot(nn,yy,pch=19,xlab='sequential heads',ylab='Proportion')
abline(h=0.05,lty=3)
f(9)
f(10)