```ts
export function stepsOn(first: number, count: number): number[] {
  const sequence: number[] = [];
  for (let i = first; i < first + count; i++) {
    sequence.push(i);
  }
  return sequence;
}

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