Recursively generating all the possible calculations between set elements in Python

I've a trouble understanding why the following recursive code (function count()) gives the wrong count of calculations, but the one based on manually written nested for loops (function count2()) gives the right count, which is n! * 4 ^ (n-1)?

(Never mind the output variable at this point. I'll use it later, if I can solve this puzzle first.)

I wish to create a recursive function that can create the calculations for a list of arbitrary length, which is why simply nesting for loops is not good enough.

import itertools
import operator
# http://stackoverflow.com/questions/2983139/assign-operator-to-variable-in-python
ops = {
    0: operator.add,
    1: operator.sub,
    2: operator.mul,
    3: operator.truediv
}
comb = [4, 1, 2, 3]
perms = list()
# itertools.permutations is not subscriptable, so this is a mandatory step.
# See e.g. http://stackoverflow.com/questions/216972/in-python-what-does-it-mean-if-an-object-is-subscriptable-or-not
# for details.
for i in itertools.permutations(comb):
    perms.append(i)
output = list()
output2 = list()

# In theory, there are n! * 4 ^ (n-1) possibilities for each set.
# In practice however some of these are redundant, because multiplication and
# addition are indifferent to calculation order. That's not tested here;
# nor is the possibility of division by zero.

# Variable debug is there just to enable checking the calculation count;
# it serves no other purpose.
debug = list()
debug2 = list()

def count(i):
    for j in range(len(i)):
        for op in ops:
            if j+1 < len(i):
                res = ops[op](i[j], i[j+1])
                if j+2 < len(i):
                    ls = list(i[j+1:])
                    ls[0] = res
                    count(ls)
                else:
                    debug.append([len(i), i[j], ops[op], i[j+1], res])
                    if res == 10: output.append(res)

def count2(i):
    for j in range(len(i)):
        for op in ops:
            if j+1 < len(i):
                res = ops[op](i[j], i[j+1])
                for op2 in ops:
                    if j+2 < len(i):
                        res2 = ops[op2](res, i[j+2])
                        for op3 in ops:
                            if j+3 < len(i):
                                res3 = ops[op3](res2, i[j+3])
                                debug2.append(res3)
                                if res3 == 10: output2.append(res3)

for i in perms:
    count(i)
    count2(i)
print(len(debug)) # The result is 2400, which is wrong.
print(len(debug2)) # The result is 1536, which is correct.