A quick and dirty notebook to generate all the Gel'fand-Tsetlin patterns and corresponding Weyl tableaux for any irreducible representation (irrep) of the Lie group of n×n unitary matrices, U(n). These notebooks were written in Mathematica 5.1 but  should work in Mathematica 3.0 and up with a little coaxing. To get them to work just evaluate the cell in the unitary_group_gelfand.nb notebook (containing the necessary subroutines). The second notebook, gelfand_eg.nb contains examples.
(Spelling and lingo variations: Gelfand, Gel Fand, Zetlin, Cetlin, semistandard, semi-standard, semi standard, Young, tableau).
unitary_group_gelfand.nb
gelfand_eg.nb