A Treble will get you two darts at a Double, but you can also reach a Double with two Singles.
61 – 80: Treble-Double or Single-Single-Double or Single Bull-Double
81 – 90: Treble-Double or Single-Single-Double Bull or Double Bull-Double
90 | 89 | 88 | 87 | 86 | 85 | 84 | 83 | 82 | 81 |
80 | 79 | 78 | 77 | 76 | 75 | 74 | 73 | 72 | 71 |
70 | 69 | 68 | 67 | 66 | 65 | 64 | 63 | 62 | 61 |