Set Partitions
In this website are resources on counting set partitions and related structures.
How can I calculate these numbers?
Where can I learn more?
Partitions into blocks
Bell numbers
- Bell number - no restriction
- Associated Bell number - elements per block
- Restricted Bell number - elements per block
- r-Bell number - the first elements are in separate blocks
- (S, r)-Bell number - the first elements are in separate blocks, block cardinality in some set
Stirling numbers
- Stirling number of the 2nd kind - blocks
- Associated Stirling number 2nd kind - blocks and elements per block
- Restricted Stirling number 2nd kind - blocks and elements per block
- r-Stirling number 2nd kind - blocks, the first elements are in separate blocks
- Restricted r-Stirling number 2nd kind - blocks, the first elements are in separate blocks, elements per block
- Associated r-Stirling number 2nd kind - blocks, the first elements are in separate blocks, elements per block
- (S, r)-Stirling number 2nd kind - blocks, the first elements are in separate blocks, block cardinality in some set
- Reduced Stirling number 2nd kind - blocks, elements with pairwise distance are in separate blocks
Restriction on the block structure
Other restrictions
Partitions into lists
Lah numbers
- Lah-Bell number - no restrictions
- Lah number - lists
- r-Lah number - lists, first elements in different lists
- r-Lah-Bell number - first elements in different lists
- Restricted r-Lah number - first elements in different lists, at most items per list
- (S, r)-Lah-Bell number - list cardinality contained in some set , first elements in different lists
- (S, r)-Lah number - lists, list cardinality contained in some set , first elements in different lists
Ordered partitions into blocks
Fubini numbers
- Fubini number - no restrictions
- (S, r)-Fubini number - block cardinality contained in some set , first elements in different blocks
Ordered partitions into lists
- Doubly ordered (S, r)-partitions - list cardinality in some set , first elements in different lists
João Costa
jpbotelho.costa at gmail dot com