you could try
  foo[t_, n_] := Module[{s, z},
    z = Array[t, n];
    s = (Plus @@ (z[[2 ;; n - 1]])) (g[Sequence @@ z]/(z[[n]] + z[[1]]));
    Integrate[s, Sequence @@ ({#, 0, Infinity} & /@ z)]
    ]
For example
  Grid[Table[{k, foo[t, k]}, {k, 3, 6}], Alignment -> Left]

You can change the indexing as needed.