===== Answer =====

x = 72

Each number in the sequence is flanked by prime numbers \\
|  3   |  **4**   |  5   |
|  5   |  **6**   |  7   |
|  11  |  **12**  |  13  |
|  17  |  **18**  |  19  |
|  29  |  **30**  |  31  |
|  41  |  **42**  |  43  |
|  59  |  **60**  |  61  |
|  71  |  **x**  |  73  |
|  101 |  **102** | 103  |