RemoveNb.js

(() => {

const range = (num) => {
	return [...Array(num).keys()].map(n => n+1)
}

const productEqualsSum = (a, b, number) => {
  const sum = ((number * (number+1)) / 2) - (a+b);
  return a*b === sum;
}

const getPair = (numbers, n) => {
	let clone = numbers.slice(0);
  let result = [];
	
  for (let a of numbers) {
  	if (result.length > 0) {
    	break;
  	}
    
    for (let b of clone) {
    	if (b+1 > numbers[numbers.length - 1]) {
      	break;
      }
      
      if (productEqualsSum(a, b+1, n)) {
      	result = [a, b+1];
        break;
      }
    }
		clone.shift();
  }
  
  return result;
}

const mirrorPair = (pair) => {
	return [pair, pair.slice().reverse()];
}

function removeNb (n) {
	let numbers = range(n);
  let pair = getPair(numbers, n);
  return (!pair.length) ? pair : mirrorPair(pair);
}

return removeNb(300);
	

})()