AS3 create multiple arrays in loop

var variants = createVariants(6, 15, 12);

// use your variations: // variants[0][0] is the same as your variant_1[0]

function createVariants(numVariants : int, numPrefilled : int, numEmpty : int) : Array{
  var variants : Array = [];
  for(var i : int = 0;i<numVariants;i++){
    var variant : Array = [];
    for(var j : int = 0;j<numPrefilled ;j++){
      variant.push(rp.getNum());
    }
    for(var j : int = 0;j<numEmpty ;j++){
      variant.push("");
    }
    variants.push(variant);
  }
  return variants;
}

Building off Paul's answer, you could also use a 2d array to store each array, with the benefit of being able to use a loop to create as many array variants as you need (cost would be the added complexity of having to maintain a 2d array).

Using a 2d array could be like:

function createArrayVarient(){
    var result:Array = new Array();
    var counter:int;

    // 15 as there are 15 numbers added first
    for(counter = 0; counter < 15; counter++){
        result.push(rp.getNum());
    }

    // 12 for the number of "" added
    for(counter = 0; counter < 12; counter++){
        result.push("");
    }
    return result;
}

var arrayVarients:Array = new Array();

// 6 as you have 6 array variants in your sample
for(var counter = 0; counter < 6; counter++){
    arrayVarients.push(createArrayVarient());
}

then if you haven't worked with 2d arrays before, to access each array varient inside "arrayVarients", it would go:

arrayVarients[0] // the first array variant
arrayVarients[1] // the second array variant
arrayVarients[2] // the third array variant
...etc

to access each value inside an array variant, it would go (using 2 indexes):

arrayVarients[0][0] // the first value in the first variant array
arrayVarients[2][7] // the eight value in the third variant array

I guess this is what you want

var iVariantCount:int = 6;//number of variants
var arrVariants:Array = new Array();//this will hold your variants array (variant_1,variant_2,etc)
var iVariantLength:int = 27;//total no fo elements in a variant array
var iRandomNumCount:int = 15;//no of random numbers in a variant array

for (var i:int = 0;  i<iVariantCount ; i++) 
{
    var arrVariant:Array = new Array();
    for (var j:int = 0;  j < iVariantCount ; j++) 
    {
        if (i < iRandomNumCount)
        {
            arrVariant.push(rp.getNum());
        }
        else
        {
            arrVariant.push("");
        }
        arrVariants.push(arrVariant);
    }   
}

//Check the result
for (i = 0;  i<arrVariants.length ; i++) 
{
    trace("Variant_" + i + ": " + arrVariants[i]);
}

Try this and tell me if it works for you.