```ts
export function stepsOn(first: number, count: number): number[] {
  if (count <= 0) throw new Error("Count must be positive");
  return Array.from({ length: count }, (_, i) => first + i);
}

export function holeFind(seen: number[], first: number, count: number): number | undefined {
  const sequence = stepsOn(first, count);
  for (let i = 0; i < sequence.length; i++) {
    if (!seen.includes(sequence[i])) return sequence[i];
  }
  return undefined;
}
```