キュムラントの計算

p[a_, b_] := Log[q[a, b]]

u = D[D[p[a, b], {a, 2}], {b, 1}]

Together[u]

p[a_, b_, c_] := Log[q[a, b, c]]
u = D[D[D[p[a, b, c], {a, 1}], {b, 1}], {c, 1}]

Together[u]

p[a_, b_, c_, d_] := Log[q[a, b, c, d]]
u = D[D[D[D[p[a, b, c, d], {a, 1}], {b, 1}], {c, 1}], {d, 1}]

Together[u]