Stage: 3 Challenge Level: 
Explain why the arithmetic sequence
1, 14, 27, 40, ...
contains many terms of the form 222...2 where only the digit 2 appears. How many twos appear in these terms?
Divisibility. Integers. Workshop. Multiplication & division. Number - generally. Factors and multiples. Sequences. Modulus arithmetic. Working systematically. Properties of numbers.
Published February 2000.
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