In mathematics, Catalan's problem asks the number of ways n + 1 factors can be completely parenthesized by n pairs of parentheses. For example, the following are the 14 ways that 5 factors can be parenthesized:
- (1 (2 (3 (4 5))))
- (1 (2 ((3 4) 5)))
- (1 ((2 3) (4 5)))
- (1 ((2 (3 4)) 5))
- (1 (((2 3) 4) 5))
- ((1 2) (3 (4 5)))
- ((1 2) ((3 4) 5))
- ((1 (2 3)) (4 5))
- ((1 (2 (3 4))) 5)
- ((1 ((2 3) 4)) 5)
- (((1 2) 3) (4 5))
- (((1 2) (3 4)) 5)
- (((1 (2 3)) 4) 5)
- ((((1 2) 3) 4) 5)
The numbers of ways of performing these pairings are the Catalan numbers.
Famous quotes containing the words catalan and/or problem:
“God forgives the sin of gluttony.”
—Catalan proverb, quoted in Colman Andrews, Catalan Cuisine.
“The problem of the novelist who wishes to write about a man’s encounter with God is how he shall make the experience—which is both natural and supernatural—understandable, and credible, to his reader. In any age this would be a problem, but in our own, it is a well- nigh insurmountable one. Today’s audience is one in which religious feeling has become, if not atrophied, at least vaporous and sentimental.”
—Flannery O’Connor (1925–1964)