Answer:
/*
I don't know what language you're using, so I'll write it in javascript which is usually legible enough.
*/
console.log(buildSequence(30));
function buildSequence(maxVal){
maxVal = Math.abs(maxVal);
var n, list = [];
for(n = 1; n < maxVal; n++){
/*
to check for odd numbers, we only need to know if the last bit
is a 1 or 0:
*/
if(n & 1){ // <-- note the binary &, as opposed to the logical &&
list[list.length] = n;
}else{
list[list.length] = -n;
}
}
return list.implode(',');
}
