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function combine(a, min) {
    var fn = function(n, src, got, all) {
        if (n == 0) {
            if (got.length > 0) {
                all[all.length] = got;
            }
            return;
        }
        for (var j = 0; j < src.length; j++) {
            fn(n - 1, src.slice(j + 1), got.concat([src[j]]), all);
        }
        return;
    }
    var all = [];
    for (var i = min; i < a.length; i++) {
        fn(i, a, [], all);
    }
    all.push(a);
    return all;
}

function arr_sum(arr) {
    var n = 0;
    for (var i = 0; i < arr.length; i++) {
        n += arr[i];
    }
    return n;
}
k=[1,2,3,4,5,6,7];
combine(k, 1).filter(function(v, i) {
    return 14 == arr_sum(v)
})