HP Prime Graphing Calculator - Manual (Page 329)

Functions and commands 323
Matrix
These functions work on matrix data stored in matrix
variables. They are explained in detail in chapter 25,
“Matrices”, beginning on page 463.
Special
Beta Returns the value of the beta function ( for two numbers a
and b.
Beta(a,b)
Gamma Returns the value of the gamma function ( for a number a.
Gamma(a)
Psi Returns the value of the nth derivative of the digamma function
at x=a, where the digamma function is the first derivative of
ln((x)).
Psi(a,n)
Zeta Returns the value of the zeta function (Z) for a real x.
Zeta(x)
erf Returns the floating point value of the error function at x=a.
erf(a)
erfc Returns the value of the complementary error function at x=a.
erfc(a)
Ei Returns the exponential integral of an expression.
Ei(Expr)
Si Returns the sine integral of an expression.
Si(Expr)
Ci Returns the cosine integral of an expression.
Ci(Expr)