Functions for grouping together elements of lists. Here is a list. This groups the elements of the list in pairs, throwing away the single element left at the end.

Partitions[n] constructs all partitions of integer n in reverse lexicographic order. Partitions[n, k] constructs all partitions of the integer n with maximum part at most k, ...

Gather[list] gathers the elements of list into sublists of identical elements.Gather[list, test] applies test to pairs of elements to determine if they should be considered ...

GatherBy[list, f] gathers into sublists each set of elements in list that gives the same value when f is applied.GatherBy[list, {f_1, f_2, ...}] gathers list into nested ...

Ways to construct nested lists. This generates a table corresponding to a 2×3 nested list. This generates an array corresponding to the same nested list.

CommunityStructureAssignment[g] gives the assignment of vertices of a graph g into communities.

ImageAssemble[{{image_11, image_12, ...}, {image_21, ...}, ...}] assembles a single image from an array of images.

BellB[n] gives the Bell number B_n. BellB[n, x] gives the Bell polynomial B_n (x).

Multinomial[n_1, n_2, ...] gives the multinomial coefficient (n_1 + n_2 + ...)!/(n_1! n_2! ...).

FindClusters[{e_1, e_2, ...}] partitions the e i into clusters of similar elements. FindClusters[{e_1 -> v_1, e_2 -> v_2, ...}] returns the v_i corresponding to the e i in ...