538's Riddler

stars.js

for(let i = 52; true; i += 2) {
	if(isGood(i)) {
		console.log(i);
		break;
	}
}

function isGood(i) {
	let sq = i / 2;
	if(!Number.isInteger(Math.sqrt(sq))){
		return false;
	}
	
	i *= 2;
	i /= 5;
	sq = Math.floor(Math.sqrt(i));
	return sq * (sq + 1) == i;
}