CatalanNumber
✖
CatalanNumber
Details

- CatalanNumber[n] is generically defined as
.
- Catalan numbers are integers for integer arguments, and appear in various tree enumeration problems.
- CatalanNumber can be used with Interval and CenteredInterval objects: »
Examples
open allclose allBasic Examples (1)Summary of the most common use cases
Scope (9)Survey of the scope of standard use cases

https://wolfram.com/xid/0h2j5ualky-8ewib

Evaluate for half-integer arguments:

https://wolfram.com/xid/0h2j5ualky-guht16


https://wolfram.com/xid/0h2j5ualky-babhg1

Evaluate for complex arguments:

https://wolfram.com/xid/0h2j5ualky-b3fbzz

Plot the Catalan number as a function of its index:

https://wolfram.com/xid/0h2j5ualky-bhunzp

Compute sums involving CatalanNumber:

https://wolfram.com/xid/0h2j5ualky-gflx9


https://wolfram.com/xid/0h2j5ualky-ep6hp5

CatalanNumber threads element-wise over lists:

https://wolfram.com/xid/0h2j5ualky-cfo

CatalanNumber can be used with Interval and CenteredInterval objects:

https://wolfram.com/xid/0h2j5ualky-h0d6g


https://wolfram.com/xid/0h2j5ualky-dj6d9x

TraditionalForm typesetting:

https://wolfram.com/xid/0h2j5ualky-blh9hi

Applications (3)Sample problems that can be solved with this function
Compute the number of different ways to parenthesize an expression:

https://wolfram.com/xid/0h2j5ualky-enq
Distribute over lists in CirclePlus:

https://wolfram.com/xid/0h2j5ualky-dqv
Use the pattern matcher to repeatedly split the list into two parts in all possible ways:

https://wolfram.com/xid/0h2j5ualky-x70

The number of ways to parenthesize the expression a⊕b⊕c⊕d:

https://wolfram.com/xid/0h2j5ualky-i2h


https://wolfram.com/xid/0h2j5ualky-cnb

The Catalan numbers CatalanNumber[n] can be characterized as the unique set of numbers such that two Hankel determinants are both equal to one. Verify for the first few cases:

https://wolfram.com/xid/0h2j5ualky-dugbf1

Verify an expression for the Catalan numbers in terms of double factorials:

https://wolfram.com/xid/0h2j5ualky-e9b7oz

Properties & Relations (6)Properties of the function, and connections to other functions
The generating function for Catalan numbers:

https://wolfram.com/xid/0h2j5ualky-bblsy4


https://wolfram.com/xid/0h2j5ualky-qux


https://wolfram.com/xid/0h2j5ualky-u7ykh

Catalan numbers can be represented as a difference of binomial coefficients:

https://wolfram.com/xid/0h2j5ualky-jipzpu


https://wolfram.com/xid/0h2j5ualky-db0scr


https://wolfram.com/xid/0h2j5ualky-h4sffw

Catalan numbers can be represented in terms of the generalized Bell polynomial:

https://wolfram.com/xid/0h2j5ualky-k486ix


https://wolfram.com/xid/0h2j5ualky-cbm2o0

CatalanNumber can be represented as a DifferenceRoot:

https://wolfram.com/xid/0h2j5ualky-pxkma

FindSequenceFunction can recognize the CatalanNumber sequence:

https://wolfram.com/xid/0h2j5ualky-hj2mn6


https://wolfram.com/xid/0h2j5ualky-5okec

The exponential generating function for CatalanNumber:

https://wolfram.com/xid/0h2j5ualky-gaiyeu

Possible Issues (1)Common pitfalls and unexpected behavior
The Catalan number is, by convention, defined using its representation in terms of binomials:

https://wolfram.com/xid/0h2j5ualky-fhp27j

This value is different from the limiting value of the analytic function:

https://wolfram.com/xid/0h2j5ualky-fjb7gu


https://wolfram.com/xid/0h2j5ualky-hjb7ed

Neat Examples (2)Surprising or curious use cases
The only odd Catalan numbers are those of the form CatalanNumber[2k-1]:

https://wolfram.com/xid/0h2j5ualky-hjl

Determinants of Hankel matrices made out of sums of Catalan numbers:

https://wolfram.com/xid/0h2j5ualky-lcdq4a

Compare with an expression in terms of the Fibonacci numbers:

https://wolfram.com/xid/0h2j5ualky-bkncvm

Wolfram Research (2007), CatalanNumber, Wolfram Language function, https://reference.wolfram.com/language/ref/CatalanNumber.html (updated 2014).
Text
Wolfram Research (2007), CatalanNumber, Wolfram Language function, https://reference.wolfram.com/language/ref/CatalanNumber.html (updated 2014).
Wolfram Research (2007), CatalanNumber, Wolfram Language function, https://reference.wolfram.com/language/ref/CatalanNumber.html (updated 2014).
CMS
Wolfram Language. 2007. "CatalanNumber." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/CatalanNumber.html.
Wolfram Language. 2007. "CatalanNumber." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/CatalanNumber.html.
APA
Wolfram Language. (2007). CatalanNumber. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CatalanNumber.html
Wolfram Language. (2007). CatalanNumber. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CatalanNumber.html
BibTeX
@misc{reference.wolfram_2025_catalannumber, author="Wolfram Research", title="{CatalanNumber}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/CatalanNumber.html}", note=[Accessed: 29-April-2025
]}
BibLaTeX
@online{reference.wolfram_2025_catalannumber, organization={Wolfram Research}, title={CatalanNumber}, year={2014}, url={https://reference.wolfram.com/language/ref/CatalanNumber.html}, note=[Accessed: 29-April-2025
]}