Check if n is divisible by 2
if ( n % 2 == 0 ) { List < int > div_by_2 = find_sequence ( n / 2 ) ; if ( div_by_2 [ 0 ] < ans [ 0 ] ) { ans . Clear ( ) ; ans . Add ( div_by_2 [ 0 ] + 1 ) ; ans . Add ( n / 2 ) ; } }