what number should replace the question mark ? 2 , 16 , 4 , 14 , 6 , 12 , - - - ?
answer : a 2 , 16 , 4 , 14 , 6 , 12 , 8 ? there are two alternate sequences : + 2 and - 2 .
add(add(add(2, 2), 2), const_2)