Starting with the circle containing 1, successively jump 1, 2, and 3 units in a horizontal or vertical direction to place the next number. Each circle should contain a number, and no numbers should be placed outside circles. The first puzzle is solved as an example.

1. | 2. | 3. | 4. | 5. |

6. | 7. | 8. | 9. |

10. | 11. | 12. | 13. |

14. | 15. | 16. |

The solutions are here.