mathball/lib/carmichael/index.js

A JavaScript library for Competitive Programming

'use strict';

/* Carmichael Number
* Function: isCarmichael()
*/

var validate = require('../validation/positive-integer');
var prime = require('../prime').check;

function squarefree(i) {
	for (var k = 2; k <= Math.sqrt(i) && i % k !== 0 && i / k % k !== 0; k++) {
		return true;
	}
}

function isCarmichael(n) {
	var c = 0;
	for (var i = 1; i <= n; i++) {
		if (n % i == 0) {
			if (prime(i) && (n - 1) % (i - 1) == 0) {
				c++;
				if (c >= 3 && i % 2 != 0 && squarefree(i)) {
					return true;
				}
			}
		}
	}
	return false;
}
exports.check = function (n) {
	validate(n, 'isCarmichael');
	return isCarmichael(n);
};