This gives the exact p-value
x_odds=50
n=75
p0=.5
binom.test(x_odds, n, p0, alternative = "greater")##
## Exact binomial test
##
## data: x_odds and n
## number of successes = 50, number of trials = 75, p-value =
## 0.002614
## alternative hypothesis: true probability of success is greater than 0.5
## 95 percent confidence interval:
## 0.5665713 1.0000000
## sample estimates:
## probability of success
## 0.6666667