021.cpp File Reference

Evaluate the sum of all amicable pairs under 10000. More...

#include <iostream>

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Classes
class	lookup_table
exception	lookup_table::k
Functions
unsigned	factor (unsigned *N, unsigned k0=3)
unsigned	term (unsigned p, unsigned k)
unsigned	d (unsigned N)
int	main ()
Variables
return	x [k]

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Detailed Description

Evaluate the sum of all amicable pairs under 10000.

Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n). If d(a) = b and d(b) = a, where a b, then a and b are an amicable pair and each of a and b are called amicable numbers. For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220. Evaluate the sum of all the amicable numbers under 10000.

Definition in file 021.cpp.