| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 2 |
| 5 | 15 |
| 6 | 42 |
| 7 | 421 |
| 8 | 1331 |
| 9 | 15119 |
| 10 | 618765 |
| 11 | 2155578 |
| 12 | 98032875 |
| 13 | 1290154807 |
| 14 | 4682196239 |
| 15 | 63117678751 |
| 16 | 3186252107917 |
| 17 | 164886529617695 |
| 18 | 616630679090258 |
| 19 | 32763760653353135 |
| 20 | 467443761039641135 |
| 21 | 1768227793278781667 |
| 22 | 96699391743949360451 |
| 23 | 1402535447576150395335 |
[1,2,15,42,421,1331,15119,618765,2155578,98032875, 1290154807,4682196239,63117678751,3186252107917, 164886529617695,616630679090258,32763760653353135, 467443761039641135,1768227793278781667, 96699391743949360451,1402535447576150395335] |