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.