The word appears 1 times.
Actually the word of choice in this novel is "coon". The word nigger doesn't appear until a fight scene in the showers, and then only once, and as a provocation.
"McMurphy," he said, shaking his head. "Y'know I was begginin' to think we might never get down to it."
"You goddamned coon," McMurphy said, somehow sounding more tired than mad. The black boy didn't say anything. McMurphy raised his voice. "Goddamned motherfucking nigger!"
The black boy shook his head and giggled at his two buddies. "What you think Mr. McMurphy is drivin' at with that kind of talk, man? You think he wants me to take the initiative? Heeheehee. Don't he know we trained to take such awful-soundin't insults from these crazies?"