Not to be confused with Ball bearing. Bearing balls are special highly spherical and smooth balls, most commonly used in ball bearings, but also used as components in things like freewheel mechanisms. The balls come in many different grades.
Euler Prime. Let a prime number generated by Euler's prime-generating polynomial be known as an Euler prime. Then the first few Euler primes occur for , 2, ..., 39, 42, 43, 45, ... (OEIS A056561), corresponding to the primes 43, 47, 53, 61, 71, 83, 97, 113, 131, 151, 173, ... (OEIS A005846).
Eulerian Number. The Eulerian number gives the number of permutations of having permutation ascents (Graham et al. 1994, p. 267). Eulerian numbers are implemented as Eulerian[n, k] in the Wolfram Language package Combinatorica` . Note that a slightly different definition of Eulerian number is used by Comtet (1974), who defines the Eulerian number (sometimes also denoted ) as the number of permutation runs of length , and hence .