What is the next number in each of the following 3 sequences?

8    17    33     67     133     ?    (1)

7    23    67     203   607     ?    (2)

6    27    105   423   1689   ?    (3)

(1) 8 → 17 → 33 → 67 → 133 → ?
Pattern: ×2 +1, ×2 −1, ×2 +1, ×2 −1, …
Next: 133×2 + 1 = 267

(2) 7 → 23 → 67 → 203 → 607 → ?
Pattern: ×3 +2, ×3 −2, ×3 +2, ×3 −2, …
Next: 607×3 + 2 = 1823

(3) 6 → 27 → 105 → 423 → 1689 → ?
Pattern: ×4 +3, ×4 −3, ×4 +3, ×4 −3, …
Next: 1689×4 + 3 = 6759

✅ Answers: (1) 267, (2) 1823, (3) 6759