list_ = [2,4,4,3,7,10,9]
i = 0
while i <= len(list_) - 1:
    if list_[i] % 2 == 0:
        try:
            if list_[i + 1] != list_[i]:
                list_.insert(i, list_[i])
            i += 2
        except IndexError:
            break
    else:
        i += 1