(mathematics) A number which results from the summation of consecutive triangular numbers, starting from 1. If the triangular numbers in such a summation are depicted as horizontal triangular arrays of units then these arrays can be stacked vertically to yield a tetrahedral array.

plural of cyclomatic number

plural of nonhypotenuse number

plural of Lucas number

plural of Bell number

(combinatorics) Any member of a sequence of numbers that count the possible partitions of a set, such that the nth number Bₙ is the number of different ways to partition a set that has exactly n elements.

(mathematics) Any of a class of coefficients expressing rising factorials in terms of falling factorials.

plural of Lah number

An identification number engraved on a disc and worn, formerly used for identification of Inuit individuals in Canada.

(geometry) For a given space, the maximum number of non-overlapping unit spheres that can be arranged in that space such that they each touch a common unit sphere.