function legoBlocks(h, w) {
    // Write your code here
    let mod = (Math.pow(10, 9) + 7)

    //different combinations for a width when height is 1
    let t = [0];
    if (w >= 1) t.push(1)
    if (w >= 2) t.push(2)
    if (w >= 3) t.push(4)
    if (w >= 4) t.push(8)
    while (w >= 5 && t.length <= w){
        let start = t.length -4
        let arr = t.slice(start, t.length)
        let sum = arr.reduce((partialSum, a) => partialSum + a, 0)
        t.push(sum)
    }

    //different combinations for width given height h
    //e.g. total[height=2] is t^2, total[height=3] is t^3
    let total = t.slice()
    for (let outer=2; outer<=h; outer++) {
        for (let i = 0; i <= w; i++) {
            total[i] = (t[i] * total[i])
        }
    }


    let solid = []
    solid.length = w+1;
    solid.fill(0)
    solid[1] = 1

    //s[x] = total[x] - (SUM (where i starts at 1 and ends at x-1)  s[i] * total[w-i]))
    if (w>1){
        for (let ww=2; ww<=w; ww++){
            let unsolid_sum = 0;
            for (let i=1; i<ww; i++){

                unsolid_sum += (((solid[i]) * (total[ww-i])))
            }
            solid[ww] = ((total[ww] - unsolid_sum))
        }
    }