Stage: 4 Challenge Level: 
Explore the factors of the numbers which are written as 10101 in different number bases.
Prove that the numbers 10201, 11011 and 10101 are composite in any base.
Mathematical reasoning & proof. Divisibility. Modulus arithmetic. Integers. Place value. epsilons. Geometric sequence. Number bases. Index notation/Indices. Factors and multiples.
Published September 1998.
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