1, 2, 3, 2, 1, 2, 3, 4, 2, 1, 2, 3, 4, 3, 2, 3, 4, 5, 3, ...
: 1, 2, 3, 2, 1, 2, 3, 4, 2, 1, 2, 3, 4, 3, 2, 3, 4, 5, 3, ...
SPOILER
The nth number in the sequence is the number of letters in the corresponding
Roman numeral (I, II, III, IV, V, ... yield 1, 2, 3, 4, 1, ...). Thus the next
number in the sequence is 2 (for XX = 20).
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__/\\ //\__ Ilan Mayer
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/__ __\ Toronto, Canada
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