Chowla numbers: Difference between revisions
define methods
(add Java implementation) |
(define methods) |
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Line 1,575:
public static void main(String[] args) {
int[]
for (int i =
System.out.printf("chowla(%d) = %d%n", (i+1),
}
System.out.println();
int[][]
System.out.printf(Locale.US, "There
for (n = 2; n <= limit; n++) {▼
System.out.println();
int[] perfectNumbers = findPerfectNumbers(35_000_000);
for (int i = 0; i < perfectNumbers.length; i++) {
System.out.printf("%d is a perfect number%n", perfectNumbers[i]);
System.out.printf(Locale.US, "There are %d perfect numbers < %,d%n", perfectNumbers.length, 35_000_000);
}
public static int chowla(int n) {
if (n < 0) throw new IllegalArgumentException("n is not positive");
for (int i = 2, j; i * i <= n; i++)
if (n % i == 0) sum += i + (i == (j = n / i) ? 0 : j);▼
return sum;
}
protected static int[][] countPrimes(int power, int limit) {
int count = 0;
int[][] num = new int[countMultiplicity(limit, power)][2];
▲ for (int n = 2, i=0; n <= limit; n++) {
if (chowla(n) == 0) count++;
if (n % power == 0) {
num[i][1] = count;
i++;
power *= 10;
}
}
}
protected static int countMultiplicity(int limit, int start) {
int count = 0;
int cur = limit;
while(cur >= start) {
count++;
cur = cur/10;
}
return count;
}
protected static int[] findChowlaNumbers(int limit) {
int[] num = new int[limit];
for (int i = 0; i < limit; i++) {
num[i] = chowla(i+1);
}
return num;
}
protected static int[] findPerfectNumbers(int limit) {
int count = 0;
int[] num = new int[count];
▲ count = 0;
▲ limit = 35000000;
int k = 2, kk = 3, p;
while ((p = k * kk) < limit) {
if (chowla(p) == p - 1) {
num[count++] = p;
}
k = kk + 1;
kk += k;
}
return num;
▲ System.out.printf(Locale.US, "There are %d perfect numbers < %,d%n", count, limit);
}
▲ if (n % i == 0) sum += i + (i == (j = n / i) ? 0 : j);
▲ return sum;
}
}
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