[Dilettante_Pro]

с большей вложенностью?

Попробовал...

var a = [6,3,1,4,2,7,5,0,9,8], k = 7;

function f(a, k) {
  return a[a[a[a[a[a[a[a[a[a[a[k]]]]]]]]]]];
}

alert(f(a,k));

var a = [6,3,1,4,2,7,5,0,9,8], k = 7;

function f(a, k) {
  return a[a[a[a[a[a[a[a[a[a[a[k]]]]]]]]]]];
}

alert(f(a,k));

var a = [6,3,1,4,2,7,8,0,9,5], k = 4;

function f(a, k) {
  return a[a[a[a[a[a[a[a[a[a[a[k]]]]]]]]]]];
}

alert(f(a,k));

var a = [6,3,1,4,2,7,5,0,9,8], k = 9;

function f(a, k) {
  return a[a[a[a[a[a[a[a[a[a[a[k]]]]]]]]]]];
}

alert(f(a,k));