It was 2am and Sergeant Sequence had been called in to Headquarters urgently. The second he stepped through the door a file was pressed into his hands by the Chief Investigator, who began to talk extremely fast while steering him towards a side-corridor.
“Patrick Terne is at it again. Triple poisoning this time – arsenic – huge quantities of it; he wasn’t taking any chances. Fled London, hopped about all over the world, but the trail’s gone cold. We traced him through eleven different countries but he’s gone totally off grid. Of course, we suspect there is some kind of pattern to his movements – there always is – but we can’t spot it… We need your eye on this case – you know him well; if anyone can get into Terne’s mind, you can…”
It was true – Sergeant Sequence had come up against Terne on several occasions before, and each time he had been able to determine the method to his madness. Staring down at the list in his hands, Sequence pondered the countries written there…
- Vietnam
- Finland
- Portugal
- Germany
- Colombia
- Moldova
- Tonga
- Canada
- Tuvalu
- India
- Kenya
But then where…?!
After just two minutes of thought, something clicked. “He’s still in Kenya,” he said. “Send your best team out there.”
“How can you be so sure?” the Chief Investigator asked, an eyebrow raised.
“I know how this guy's mind works,” Sequence replied. “And trust me – if he’s done what I think he has it would have been impossible to make a twelfth move.”
TASK: Identify the pattern behind the sequence “Vietnam, Finland, Portugal, Germany, Colombia, Moldova, Tonga, Canada, Tuvalu, India, Kenya” and explain why it ends there.
Hint:
The sequence relies on TWO pieces of knowledge in combination.
