A = [1,3,5]
B = [2,4,6]

A = [1,3,5]
B = [2,4,6]
stored = []

#Work out the maximum  length of a valid subsequence
max_length = len(B) + len(A) - (max(len(A), len(B)) - min(len(A), len(B)))

for x in range (2, max_length + 1, 2): #Incremenet in steps of 2
    for item in A: #Take each element in A
        for start_B in range(len(B) + 1): #Gets an index so a copy of B can be made
            new_A = A[:]
            new_B = B[start_B:] #Uses index to create copy of B starting from start_B
            output_array = []
            index = 0
            turnA = True
            while new_A or new_B:
                if output_array == []:
                    output_array.append(item)
                    new_A.remove(item)
                    turnA = False
                if turnA and new_A:
                    if new_A[0] > output_array[-1]:
                        output_array.append(new_A[0])
                        turnA = False
                    new_A.pop(0)
                elif turnA == False and new_B:
                    if new_B[0] > output_array[-1]:
                        output_array.append(new_B[0])
                        turnA = True
                    new_B.pop(0)
                else:
                    break
                if len(output_array) == x:
                    if output_array not in stored:
                        print(output_array)
                        stored.append(output_array[:])
                    output_array.pop()
                    if turnA == False:
                        turnA == True
                    else:
                        turnA = False