Upgrading from:

NumberTheory`Frobenius`

FrobeniusInstance and FrobeniusSolve are now available as the newly added built-in Mathematica kernel function FrobeniusSolve.
FrobeniusF is now available as the newly added built-in Mathematica kernel function FrobeniusNumber.

FrobeniusSolve

All solutions of the Frobenius equation :

Version 5.2 << NumberTheory`Frobenius`; FrobeniusSolve[{12, 16, 20, 27}, 123]

Find one solution of the Frobenius equation :

Version 5.2 << NumberTheory`Frobenius`; FrobeniusInstance[{12, 16, 20, 27}, 123]

FrobeniusNumber

The Frobenius number of 12, 16, 20, 27:

Version 5.2 << NumberTheory`Frobenius`; FrobeniusF[{12, 16, 20, 27}]