Отображение отделений HTML по Silverlight

function f(A, x){
  if (x < 0 || x > A.length - 1)
    return 0

  return l(A, x) + r(A, x)
  
  function l(A, x){
    if (x < 0 || x > A.length - 1)
      return 0
    if (x == 0)
      return 1
      
    let result = l(A, x-1)
    
    if (A[x-2] && A[x-2] == 2){
      result += l(A, x-2)

      if (A[x-3] && A[x-3] == 2)
        result += l(A, x-3)
    }
      
    return result
  }
  
  function r(A, x){
    if (x < 0 || x >= A.length - 1 || !(A[x-1] && A[x-1] == 2))
      return 0
      
    let result = l(A, x-1)
    
    if (A[x+2] && A[x+2] == 2)
      result += l(A, x-1) * f(A.slice(x+1), 1)
      
    return result
  }
}
      
        
function validate(A){
  let n = A.length
  
  function g(i, s){
    if (debug)
      console.log(s)
    let result = 1
    let [a, b] = [i+1, i-1]
    
    if (a < n && !s.includes(a))
      result += g(a, s.slice().concat(a))
    if (b >= 0 && !s.includes(b))
      result += g(b, s.slice().concat(b))
      
    if (A[i] == 2){
      [a, b] = [i+2, i-2]
    
      if (a < n && !s.includes(a))
        result += g(a, s.slice().concat(a))
      if (b >= 0 && !s.includes(b))
        result += g(b, s.slice().concat(b))
    }
    
    return result
  }
  
  return g(0, [0])
}

let debug = false

let arr = []
let n = 7
for (let i=0; i<n; i++)
  arr[i] = Math.ceil(Math.random() * 2)
console.log(JSON.stringify(arr))
console.log('')

let res = 0
for (let x=0; x<arr.length; x++){
  let c = f(arr,  x)
  if (debug)
    console.log([x, c])
  res += c
}

if (debug)
  console.log('')
let v = validate(arr)
if (debug)
  console.log('')
console.log(v)
console.log(res)