123: The Black Hole Number

  • Start with any number, say 9288759
  • Count the number of even digits, the number of odd digits, the total number of digits.
  • You get 347
  • Repeat and you get 123
  • Repeat and you get 123
  • Repeat and you get 123
  • …
  • Once you reach 123, you never get out, just as reaching a black hole in physics implies no escape.

A simple program in Node JS to test:

/*
Moncho Pena
2013-02-22
*/
var myargs = process.argv.slice(2);
if (myargs[0]) {
var number=myargs[0];
number=stripAlphaChars(number);
if (number=='') {
number=0;
}
if (number<100) {
console.log('Please use a number greater than 99');
} else {
console.log(number);
var test=convert(number);
while (test[3]!=123) {
test=convert(test[3]);
}
}
} else {
console.log('Use: node 123.js number');
}
function stripAlphaChars(source) { 
var out = source.replace(/[^0-9]/g, ''); 
return out; 
}
function convert(number) {
var numbers= new Array();
var res= new Array();
var pair=0;
var odd=0;
for (var i=0;i<number.length;i++) {
var control=number.substr(i, 1);
if ((control%2)==0) {
pair++;
} else {
odd++;
}
}
res[0]=pair;
res[1]=odd;
res[2]=number.length;
var super_number=res[0].toString()+res[1].toString()+res[2].toString();
console.log(super_number);
res[3]=super_number;
return res;
}

Running:

123.js Screenshot

I’ve read this curiosity on Gaussianos.