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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 31 |
| 3 | 111 |
| 4 | 351 |
| 5 | 1023 |
| 6 | 2815 |
| 7 | 7423 |
| 8 | 18943 |
| 9 | 47103 |
| 10 | 114687 |
| 11 | 274431 |
| 12 | 647167 |
| 13 | 1507327 |
| 14 | 3473407 |
| 15 | 7929855 |
| 16 | 17956863 |
| 17 | 40370175 |
| 18 | 90177535 |
| 19 | 200278015 |
| 20 | 442499071 |
| 21 | 973078527 |
| 22 | 2130706431 |
| 23 | 4647288831 |
| 24 | 10099884031 |
| 25 | 21877489663 |
[1,7,31,111,351,1023,2815,7423,18943,47103,114687, 274431,647167,1507327,3473407,7929855,17956863, 40370175,90177535,200278015,442499071,973078527, 2130706431,4647288831,10099884031,21877489663] |