Stage: 5 Challenge Level: 
To test whether a number is polite consider its factors and the factors in the formula for the sum of the corresponding arithmetic progression.
Generalising. Mathematical reasoning & proof. Manipulating algebraic expressions/formulae. Stage 5 - Reviewed 2012. Inequality/inequalities. Making and proving conjectures. Number theory. Factors and multiples. Arithmetic sequence. Patterned numbers.
Published November 2002,December 2002,March 2009,April 2009.
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