最初の要素に加えて、すべての要素のパワーセットから最初と最後の要素を引いたものを組み合わせたものです。
from itertools import chain, combinations
test = [0, 1, 2, 3, 4, 5]
def powerset(iterable):
"powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
s = list(iterable)
return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
print [test[:1] + list(c) for c in powerset(test[1:-1])]
# [[0], [0, 1], [0, 2], [0, 3], [0, 4], [0, 1, 2], [0, 1, 3], [0, 1, 4], [0, 2, 3], [0, 2, 4], [0, 3, 4], [0, 1, 2, 3], [0, 1, 2, 4], [0, 1, 3, 4], [0, 2, 3, 4], [0, 1, 2, 3, 4]]