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function compact_number_list(anArray){
    var len = anArray.length;
    var result = new Array();

    for(var i=0;i<len;i++){
        var seq;
        if(seq=isSequence(anArray[i], i, anArray)){
            result.push(seq);
            i += (seq[2])? (seq[1]-seq[0])/seq[2] : seq[1]-seq[0];
        } else {
            result.push(anArray[i]);
        }
    }
    return result;
}
function isSequence(el, index, array){
    var next=array[index+1];
    if(next == undefined){ return false; }

    var d = next - el;
    for(var i=0;array[index + i] == el + i * d;i++);

    if(i>2){
        return (d==1) ? [el, array[index + i -1]] : [el, array[index + i -1], d];
    } else {
        return false;
    }
}