No prob. I’m assuming you’re not looking to be taught how to fish here.
This should get it done for you.
var offset = 0 // How far to start from the left
var onCount = 5
var every = 20
export function render(index) {
  on = mod(index - offset, every) < onCount
  hsv(0, 0, on)
}
// You only need this on PB v2
function mod(dividend, divisor) {
  var res = dividend % divisor
  if ((res != 0) && (res > 0) != (divisor > 0)) { //this compares the sign of both
    res += divisor
  }
  return res
}
Edit: The guy who asked for a builtin mod() (me) forgot to use it correctly  Now it’s fixed in the above, with Wizard’s mod polyfill for v2 users.
 Now it’s fixed in the above, with Wizard’s mod polyfill for v2 users.