Meijer G-function (mpmath, SymPy, WMA)
MeijerG[${{a_1, ..., a_n}, {a_{n+1}, ..., a_p}}, {{b_1, ..., b_m}, {b_{m+1}, ..., a_q}}, z$]MeijerG[{{1, 2}, {}}, {{3}, {}}, 1]
unless a numerical evaluation is explicitly requested:
MeijerG[{{1, 2},{}}, {{3},{}}, 1] // N
MeijerG[{{1, 2},{}}, {{3},{}}, 1.]