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| n | a(n) |
|---|---|
| 1 | 7 |
| 2 | 53 |
| 3 | 330 |
| 4 | 1809 |
| 5 | 8940 |
| 6 | 41257 |
| 7 | 180670 |
| 8 | 756800 |
| 9 | 3066706 |
| 10 | 12093628 |
| 11 | 46563397 |
| 12 | 175879412 |
| 13 | 653526033 |
| 14 | 2392564820 |
| 15 | 8651185991 |
| 16 | 30941217363 |
| 17 | 109551653219 |
| 18 | 384528798543 |
| 19 | 1339204256650 |
| 20 | 4630162104037 |
| 21 | 15905909415604 |
| 22 | 54322204287215 |
[7,53,330,1809,8940,41257,180670,756800,3066706, 12093628,46563397,175879412,653526033,2392564820, 8651185991,30941217363,109551653219,384528798543, 1339204256650,4630162104037,15905909415604, 54322204287215] |