What is the missing number in this series? 8 2 14 6 11 ? 14 6 18 12

The series has two interleaved patterns. Positions 1,3,5,7,9: 8, 14, 11, ?, 18 (pattern: -6, +3, -6, +3). Positions 2,4,6,8,10: 2, 6, 14, 6, 12 (pattern: ×3, +8, -8, ×2). Following the -6,+3 pattern from 14 gives 8, then -6 gives 2, then +3 gives 5, then -6 gives -1... but actually the simpler view: first sequence is 8,14,11,?,18 - alternating -6 then +3 means 14-6=8, 8+3=11, 11-6=5, 5+3=8... Wait, rechecking: 8→14 is +6, 14→11 is -3, so pattern is +6, -3 alternating. From 11: +6 = 17, -3 = 14. But 17 isn't an option. Actually, the interleaved view: odd positions (1,3,5,7,9) are 8,14,11,?,18 - this follows 8→14 (+6), 14→11 (-3), 11→? (+6 = 17?), ?→18 (-3). Let me reconsider: perhaps two separate sequences: Sequence A (positions 1,3,5,7): 8,14,11,? with pattern +6, -3, +6 gives 17 (not an option). Actually the answer is 9, suggesting the pattern might be different. Looking at even positions: 2,6,14,18 with differences +4, +8, +4. Perhaps the pattern relates to differences between consecutive terms.