BesselJ (Built-in Mathematica Symbol)

BesselJ[n, z] gives the Bessel function of the first kind J_n (z).

CarmichaelLambda (Built-in Mathematica Symbol)

CarmichaelLambda[n] gives the Carmichael function \[Lambda](n), defined as the smallest integer m such that k^m \[Congruent] 1 mod n for all k relatively prime to n.

Ceiling (Built-in Mathematica Symbol)

Ceiling[x] gives the smallest integer greater than or equal to x. Ceiling[x, a] gives the smallest multiple of a greater than or equal to x.

CoshIntegral (Built-in Mathematica Symbol)

CoshIntegral[z] gives the hyperbolic cosine integral Chi(z).

CosIntegral (Built-in Mathematica Symbol)

CosIntegral[z] gives the cosine integral function Ci(z).

DifferentialRootReduce (Built-in Mathematica Symbol)

DifferentialRootReduce[expr, x] attempts to reduce expr to a single DifferentialRoot object as a function of x.DifferentialRootReduce[expr, {x, x_0}] takes the initial ...

DivisorSigma (Built-in Mathematica Symbol)

DivisorSigma[k, n] gives the divisor function \[Sigma]_k (n).

Erfi (Built-in Mathematica Symbol)

Erfi[z] gives the imaginary error function erf(i z)/i.

EulerE (Built-in Mathematica Symbol)

EulerE[n] gives the Euler number E_n. EulerE[n, x] gives the Euler polynomial E_n (x).

Factorial2 (Built-in Mathematica Symbol)

n!! gives the double factorial of n.